Genetic diversity can arise as a result of mutation or during meiosis

Question 1

what is a gene mutation?

Answer 1

a change in the base sequence of DNA (deletion and substitution)

Question 2

what is a mutagenic agent?

Answer 2

a factor that increases rate of gene mutation

Question 3

explain how a mutation can lead to the production of a non-functional protein or enzyme

Answer 3

1, changes sequence of base Triplet in DNA so the sequence of codons is changed on mRNA, so the sequence of amino acids in polypeptide is changed and bonds (hydrogen, ionic and disulfide bridges) are changed. so the tertiary structure is changed of a protein and enzymes active site changes shape so no ESC can form

Question 4

explain the possible effects of a substitution mutation

Answer 4

Base in DNA is replaced by a different base changing one Triplet so the mRNA codon is changed, so one amino acid changes in the polypeptide

Question 5

explain the possible effects of a deletion mutation

Answer 5

one base is removed from DNA sequence which changes the sequence of DNA Triplet therefore changing the sequence of mRNA codons, and changing the amino acid sequence in the primary structure of polypeptide - bonds change (hydrogen, ionic and disulfide) changing tertiary structure

Question 6

describe features of homologous chromosomes

Answer 6

they have the same length, same genes at the same loci, but may have different alleles

Question 7

what is a diploid

Answer 7

has 2 complete sets of chromosomes

Question 8

what is a haploid

Answer 8

has a single set of unpaired chromosomes

Question 9

describe how a cell divides by meiosis

Answer 9

1- meosis 1 the homologous chromosomes separate and chromosomes arange into homologous pairs. Crossing over between homologous chromosomes occurs - independent segregation of homologous chromosomes
2-meosis 2 separates the chromatids

Question 10

what is the outcome of meosis?

Answer 10

4 genetically varied daughter cells and are normally haploid

Question 11

explain why the number of chromosomes is halfed during meosis

Answer 11

homologous chromosomes are separated during meosis 1

Question 12

explain how crossing over creates genetic variation

Answer 12

-homologous pairs of chromosomes associate from a bivalent
-chiasmata form
-alleles are exchanged between chromosomes creating a new combination of alleles on chromosomes

Question 13

explain how independent segregation creates genetic variation

Answer 13

-homologous pairs randomly align at the equator creating a different combinations of maternal and paternal chromosomes

Question 14

how is genetic variation increased?

Answer 14

-mutations
-meosis
-random fertilisation
-creating new allele combinations

Question 15

explain the different outcomes of mitosis and meosis

Answer 15

•mitosis produces 2 daughter cells whereas meosis produces 4
•mitosis maintains the chromosome number whereas meosis halves the chromosome number
•mitosis produces genetically identical daughter cells whereas meosis produces genetically varied daughter cells

Question 16

explain the importance of meosis

Answer 16

two devision creates a haploid gamete so diploid number is restored at fertilisation

Question 17

describe how mutations in the number of chromosomes arise

Answer 17

•spontaneously by chromosome non-dusjunction during meosis