dna replication meiosis

Question 1

homologous pair

Answer 1

one pair from each parent; same gene but different alleles

Question 2

gamete

Answer 2

haploid sex cell

Question 3

haploid

Answer 3

(n)

a cell with a single set of unpaired chromosomes

(one of each homologous pair)

Question 4

diploid

Answer 4

(2n)

a cell with two complete sets of chromosomes

(both homologous pairs)

Question 5

fertilisation

Answer 5

fusion of 2 haploid cells to form a zygote

Question 6

what happens before meiosis

Answer 6

dna replication where diploid doubles its chromatids

which forms sister chromatids joined by a centromere before starting prophase I

(doesn’t change actual chromosome no.)

Question 7

difference between meiosis and mitosis

Answer 7

meiosis:

cell division to form haploid (gametes)

2 divisons => 4 daughter cells

genetically different

mitosis:

cell division for growth of organism and repair of tissues

1 division => 2 daughter cells

genteically identical

Question 8

what happens during meiosis

Answer 8

homologous chromosomes pair up

crossing over

produces new combo of alleles

chromosones sepearate at random

produces varying combos of genes

chromoarids separated at meiosis II

Question 9

two ways in genetic variation is introduced

Answer 9

Crossing over: Different combination of alleles

During metaphase I, where chromatids of homologous pairs cross over and swap alleles

(produces chiasmata: crossed over holograms pairs)

Independent segregation: different combination of chromosomes

Question 10

gene mutation

Answer 10

random change to the base sequence of DNA during DNA replication

Question 11

Substitution

Answer 11

swapping one base for a different base

Question 12

deletion

Answer 12

one or more bases is remove which causes a frame shift and changes the following triplets

Question 13

how do mutations cause a non-functional protein?

Answer 13

Change to DNA triplet during replication

Change to mRNA codon

Different anticodon => different amino acid, which changes primary structure of protein

Hydrogen, ionic and sulphate binds made in different places

Changes tertiary structure

change in active site so no e-s complexes form

Question 14

why no change to sturcture of protein

Answer 14

DNA is degenerate

Each amino acid is coded for y more than one triplet codon

Change to DNA base (substitution) might not cause a change to amino acid in primary structure

No changes to bonding, therefore also not to tertiary structure

Question 15

chromosome non-disjunction

Answer 15

when chromosomes don’t separate properly during meiosis I or meiosis II

This causes an uneven no. of chromosomes in the gametes

Genetic disease eg. Down’s syndrome

Question 17

what is a mutagenic agent

Answer 17

any sort of radiation

eg x-ray

Question 18

minor impact

Answer 18

where mutation occurs in intron/

dna is degenerate