KPK Board 12th Class Biology Ch 23 Chromosome and DNA Short Questions Answers

chromosome are third like structure in the nucleus of organism for the first time they were discovered by waldeyer.

function chromosomes controlled the heredity character of organism the number of chromosomes remains constant and specific for each species of humans 46 in the potato 48 and drosophila 8.

when the cell is not dividing it genetic material appears as the fibrous structure called chromatin Network at this stage the individual chromosomes cannot be counted unit nucleosome is the unit of chromatin.

the unit of chromatin material is called the nucleus structure in a nucleosome 200 nucleotides of duplex DNA and 8 molecule of histone form a core   of nucleosome around which two turn of about 200 nucleotides of a double helical DNA is wrapped to form a super helix.

the alternative form of a gene is called  allele .

allele are formed as a result of Nutrition.

location alleles are located on the same locus as there respective gene.

alleles cause variation.

these are the unit of heredity they play very important role due to the following reasons that transfer the character from parents to their offspring their control are definite character of organism they are able to duplicate themselves accurately  they mainly act by producing enzymes the sequence of amino acids in a protein is determined by genes.

a typical chromosome consists of a long DNA molecule centromere chromatid are attached with each other at a point known as centromere it is also known as primary construction nucleolar organiser some chromosome may have another point of union along the length of chromatin called secondary constriction are nucleolar organiser satellite beside the secondary constriction and becomes knob like structure called satellite chemically the chromosome are formed of two components DNA and protein it is the .telomere terminal end of chromosome that prevent to chromosomes to attach.

on the basis of position of centromere chromosomes are of following types metacentric in this chromosome the centromere is located at the centre submetacentric in this type centromere is slightly away from the centre acrocentric in this type centromere is near the end telocentric hair the centromere is at end.

generally a chromosome is made up of two components DNA and protein DNA it constitutes 40% and is negatively charged protein chromosomal from a protein is done and is 60% in chromosome proteins are positively charged type in chromosomes five type of histone protein are found at  H1, H2A, H3, H2B, and H4.

Arrangement about every 200 nucleotides of the blacks DNA trap twice around the core of a stone does forming a complex known as nucleosome.

this idea about hereditary units was proposed by drain in 1868 according to which circulating units called gemmules are accumulated in gonads and transferred to offspring.

Devries: in 1896 used the word for pengene of heredity.

W.Johnson in 1909 Johnson used the term gene for heredity units.

the modern concept of gene was given by Mendel according to Mendel each rate in pea plant is controlled by discrete units called factor or elements modern concept according to to modern concept of gene is composed of nucleotide sequence of a short segment of DNA which in course the sequence of amino acid of a particular polypeptide.

Gene  is a particular segment of DNA a it consists of following structural components promoter it is a regulatory region that controls the binding RNA polymerase Terminator it causes RNA polymerase to stop the transcription structural region the region between the promoter and Terminator is called the structural region that consists of genetic information introns the non functional sequence of Eukaryotic gene is called in intron.

Exxon is the functional sequence Operon in prokaryotes; many adjacent structural genes that synthesise different polypeptides are regulated by the same promoters and Terminators subgroup of gene are called Operon.

According to this theory the genes found in the chromosomes first proposed by this idea was for the first time proposed by kari correns.

1. Sutton  in 1902 and T. boveri recognised that the behaviour of mental factor is parallel to chromosome Morgan at last Morgan confirmed by his experiments on drosophila that the gene was located on chromosome.

parallel behaviour of genes and chromosomes during meiosis behaviour of chromosomes diploid cells perform meiosis have two copies of each chromosome pair will get after meiosis have only one in pea plant cell have 7 pair of homologous chromosomes will have single cell 7 chromosomes homologous pair of chromosomes segregate during meiosis during meiosis each pair of chromosomes Orient on the metaphase plate independently each pair assort independently of the other .

Behaviour of gene according to the mental diploid cell have two copies of each gene will gamete have only one in pea plant diploid cell have a pairs of alleles for each gene like a Rr or Yy or T stand will gamete have single or Rand r andY and y and T and  t according to the mental pair of gene for each trade also segregate from each other during meiosis according to the mental alleles of one gene pair also a sort independently to the allele of other gene pair during meiosis; RrYy .Genotype as a result of independent assortment can form four  type of gametesRY, ry ,rY.

DNA is the hereditary material present in the nucleus strings the Eukaryotic DNA appear asA string of beads.

Nucleosome:  every 200 nucleotide the DNA is coiled around core of eight histone protein forming a structure called nucleosome.

Histone which are positively charged protein in chromosomes and attract the negatively charged phosphate group supercoil die stone does acting as a magnetic form that promote coiling of DNA when the spring of nucleosome wraps up into higher order called supercoil heterochromatin highly condensed portion of chromatin is called the heterochromatin euchromatin : it is condensed only during division and is the remainder portion of chromosomes.

The first evidence that DNA is hereditary material was provided by Frederick griffith

griffith used Mice and bacteria for his experiment.

s form:  normal pathogenic form of bacteria in pneumonia Lake the Virulent court and theMice show no effect.

are form it is the virulent form forming rough Colony.

actual experiment griffith injected that bacteria of virulent S strain into the mice that remained perfectly healthy control experiment as a control injected mice with a mixture of dad S and live R.

Result unexpectedly the mice developed the disease and die conclusion the blood of Dead mice was found to contain virulent type living proving the same information had passed from virulence dead to non virulent does making it virulent.

the series of experiments performed by avery macleod and mccarty confirmed will Griffith was the first to suggested the bacteria are capable of transforming the genetic material through a process of transformation .

hershey and chase experiment on bacteriophage.

3P2 labelled viruses the DNA of some viruses was labelled with Phosphorus P32 and S35 labelled viruses the protein Court of some viruses were labelled as result after infection the study of both types of viruses show that only P32 was transferred to another generation proving that DNA is a hereditary material.

Protein synthesis is a genetic program for the specific linkage sequence of amino acid control DNA does not assemble the amino acid instead it worked together with RNA to form protein from amino acid steps transcription it is the formation of messenger RNA from DNAtranslation is the formation of polypeptide by messenger RNA.

it is the first step of protein synthesis following steps are involved in this DNA form a copy of single stranded RNA that is called messenger RNA decoded message on messenger RNA is called codon that contain multiple mould messenger RNA leave the nucleus and more towards ribosome ribosome begins to move from one and of strand of   messenger RNA to another end to decode the message .

Following important event take place during this process.

messenger RNA moves towards ribosomes.

Ribosome moves from one end of messenger RNA to another to decode it message.

transfer RNA carrying a specific amino acid link with matching triple anticodon ribosome continue to move along messenger RNA the next triple of base on other transfer RNA molecule come for the amino acid does bind with one another to form a polypeptide chain.

the genetic code present on messenger RNA is in the form of triple and is called codon initial codon the initial codon that start the protein synthesis is AUG.

it stop the further addition of amino acids UGA is termination codon.

terminal codon it stop the further addition of amino acids UGA is the terminal codon.

anti codon the matching tripled on transfer RNA anticodon it record the message of codon to lybrate a particular amino acid.

it is a process by which DNA of living organism give rise to a copy of itself this process occur only one in S phase during cell cycle parent DNA it is the molecule of DNA which is replicated daughter DNA molecules which are produced by the application are called daughter DNA.

the different models that explain the  replication process as following

semiconservative model: This model was given by Watson and Crick according to this model the parent DNA and rape and both strand act as template that allowed the formation of newstrends.

conservative model according to this model the parent DNA remains intact in its duplex state well a daughter DNA  molecule with both new strand is established.

dispersive model this model predicted that parental DNA would become completely dispersed into fragments which will mix with new  nucleotides fragments.

The DNA collected immediately after the transfer was all dance after bacterial completed their first round of DNA replication in in N-14 medium the density of their DNA had decreased after the second round of replication to density classes of DNA were observed one intermediate and one equal to that N- DNA.

meselson and stahl;s interpreted their result as follows.

first round after first round of replication each daughter DNA was a hybrid processing one of the heaviest and of parent molecule and one light stand.

second round when the hybrid duplex replicated it contributed one Heavy strand to form another hybrid duplex and one light stand to form a light stand duplex.

conclusion this experiment clearly confirmed The prediction of Watson and Crick model that DNA replicates in a semi conservative manner.

the basic requirements to carry out DNA replication is

template DNA

building blocks

DNA helicase single stranded binding proteins

DNA topoisomerase

DNA Primase

DNA polymerase DNA ligase

DNA polymerase 1:  DNA polymerase is relatively small in time and play Sporting role in DNA replication.

of DNA to this has our role in the repair process of DNA.

DNA polymerase 3 is the main enzyme that synthesis both daughters stand along template during replication .

 The leading strand which elongates towards the replication fork it built up simply by adding nucleotides continuously to its discontinuous replication the lagging strand with alone gets away from the replication fork is synthesized by this discontinuously a series of short segments that are later connected.

genetic code is a combination of 32 nucleotides in DNA which specify a particular amino acid.

triple code after a long research it was known that the code for specifying amino acids consists of three bases so it is called crippled code most of the amino acids are specified by more than one code reading the reading of this cold occurs continuously without punctuation between the three nucleotides units.

the study of the genetic code of mitochondrial DNA shows that the genetic code is not. Quite Universal for example.

UGA codon normally stops codon but in the mitochondrial DNA it reads as tryptophan .

Likewise AUA was read as MethionineRather than original does it appear that the genetic code is not quite universal.

leading strand it is a strand of nascent DNA which is being form in the same direction as the growing replication fork it is ready by polymerase lagging strand it is the strand of nascent DNA is direction of synthesis is opposite to the direction of growing replication fork its replication is more complicated okazaki fragments these are short newly synthesized DNA fragments that are formed by legging template strand during replication.

all organism use the same basic mechanism of reading and expressing the genes which aften referred to as Central dogma turn off the flow of genetic information with in a biological system

DNA to RNA to protein.

the removal of introns and maturation of primary messenger RNA to secondary or functional messenger RNA is called RNA splicing a newly emerged Eukaryotic messenger RNA is very long as it contains both exon and intron sequence introns are non protein coding sequence which are to be removed from the primary messenger RNA before it’s translation on the ribosomes this removal is called splicing.

activation of amino acids refers to the binding ofFree amino acids dispersed in the cytoplasm complex in this way are complex is formed called  aminoacyl  transfer RNA complex .

Enzymes this binding is catalysed by aminoacyl transfer RNA synthesis.

amino acids various amino acids that are to take part polypeptide formation have been continuously activated through the process of translation.

it is a phase of protein synthesis in which type of  ribosomal units  move along messenger RNA amino acids are brought by transfer RNA which are joined together to form a polypeptide chain steps following steps are repeated again and again from this phase codon and anticodon bind with the help of elongation factorEnzyme peptidyl transfer remove the the amino acid from transfer RNA and join it with coming amino acid with peptide Bond then ribosomal RNA slightly move along messenger RNA.

Regulation of gene expression is Gene regulation is essential for prokaryotes and eukaryotes due to the following reasons.

It increases versatility e of an organism and it also increases the  adaptability  of an organism by allowing the cell to express protein when needed it drives the process of cellular differentiation and  morphogenesis.

Gene mutation is a permanent change in the DNA sequence that makes up a new  allele in population mutagens. The agents that cause mutation are called mutation radiation viruses and Chemicals. mutant the organism in which mutation occurs is called mutant.

Hereditary mutations are the mutations that are passed from parents to child as they are present in the egg or sperm cell so they are also called Germ line mutation.

de novo mutation  mutations just after fertilization may explain genetic disorders in which an affected child has mutation in every cell but has no family history of the disorder.

acquired mutation  occurs in DNA in the individual cells at some time during a person’s life it is also called somatic mutation.

spontaneous mutation it is the mutation that occurs naturally and automatically reasons the reason for spontaneous mutation is the internal factors.

induced mutation it is the mutation which is produced by external factors.

Mutation that causes change of single few nucleotides in DNA is called point mutation.

type deletion is the removal of one are few nucleotides from a particular segment of DNA.

Insertion is the addition of one or more nucleotides in a particular segment of DNA base substitution; it is the replacement of one or few nucleotides in a particular segmentOf DNA.

The structural changes in chromosomes are called chromosomal mutations are aberrations.

types of deletion it is the removal of a segment of chromosome comprising of single are few genes inversion in this type of person of a chromosome break off turn around and join such that the the gene sequence get reversed translocation it involve shifting of a segment of one chromosome to another nonhomologous chromosomes thus both  are affected.

duplication : it is the repetition of one or few genes in the same chromosomes.

It is the change in the number of chromosomes due to addition or loss of one or  more chromosomes.monosomy it is the state of ( 2n-1) .

Nullisomy is the state of (2n-2).

Trisomy is the state of (2n+1).

Tetrasomy is the state of (2n+2).

It is the change in chromosome number due to addition or loss of a complete set of chromosomes.

It is a  condition of a cell organism having an integral multiple monoploid of chromosome  it is also called polyploid.

polyploids occur in the following forms.

Triploidy: = three sets

tetraploidy= four sets

Penta ploidy = five sets

Hexaploid = six sets

Current polyploid is common in plants but there in animals one reason is that vi balance is important in animal and variations from diploid and variations from deployed number result in sterility.

There are two basic types of mutagens physical mutagens

shortwave radiation

X-rays

Gamma and ultraviolet rays

natural radiation of Cosmic rays

Chemical mutagens nitric acid formaldehyde mustard gas S- bromouracil acridines

Nicotine food preservatives and pesticides caffeine.

it is an autosomal recessive genetic blood disorder in which abnormal rigid Sickle shaped red blood cells are seen in individuals symptoms following are the important symptoms of the disease low number of red blood cells repeated infection periodic pain fatigue delayed growth and development yellowing of eyes and skin.

Folic acid supplements blood transfusion pain Killers plenty of  fruit antibiotics to prevent infections and hydration.

is phenyl Ketonuria where condition in which  a baby born With an ability to properly breakdown

Of amino acid phenyl alanine causes it is an autosomal recessive inherited trait the PKUpatient are missing and enzyme phenylalanine hydroxylase the accumulated substances can cause brain damage symptoms lighter skin and hair colour mental skills had size below normal hyperactivity jerking movements skin rashes .

Treatment   low phenyl alanine diet .

A (special formula for PKU patients) Lofenalac.

It is a (2n+1) Condition of a person has an extra copy of 21 first chromosomes following physical character are characteristic of down syndrome flattened face and nose short neck portending tongue small hairs upward slanting eyes short hand and fingers delayed development .

it is also called(XXY syndrome) it is a condition in which human males have an extra X chromosomes symptoms important symptoms of this syndrome are weak muscles reduced Central less facial and body hair broader hips or trouble in fighting in with other kids taller than others and produce little no sperm causes it is caused by nondisjunctionOf sex chromosome of mother at always occur in males treatment testosterone replacement therapy can help males to get their testosterone level normal.

it is a chromosomal disorder of condition(44+X) it always occurs in females due to Y chromosome missing.

symptoms short stature functionalis ovaries infertility frequent middle ear infections usually normal intelligent level causes it is caused by sex chromosome non  disjunction treatment growth hormones injections estrogen and progesterone replacement therapy.

monoploid refers to  the number of chromosomes of cells meaning that two cells have only one chromosome from every n pairs (n=33)Haploid strictly refers to the number of chromosomes in germ cells .

avery;s experiment showed the changes that occur in DNA were based on some of the experiments that were done by Griffith before him; it should show how DNA is the transforming factor of all living organisms .

T Lsc lactose Operon is a functional unit of genomic DNA containing clusters of genes required for transport and metabolism of lactose.structure repressor gene it produce a repressor protein that fit in the the operator to turn Operon of promoter RNA polymerase attach to here to begin transcription operator the active repressor fit in notches  to block RNA polymerase and turn off transcription.

structure gene metabolic pathway gene with code for enzymes to digest lactose.