reproduction

Question 1

locus

Answer 1

the position of a gene on a chromosome

Question 2

chromatid

Answer 2

when DNA replicates, it forms chromosomes made of two identical sister chromatids- each containing the same copy of genes for that chromosome

Question 3

gamete

Answer 3

a haploid sex cell

Question 4

zygote

Answer 4

the diploid cell formed when 2 gametes fuse

Question 5

haploid

Answer 5

half the usual number of DNA

Question 6

diploid

Answer 6

cell containing a complete set of DNA

Question 7

Reasons for variation between organisms that reproduce sexually

Answer 7

meiosis and random fertillisation

Question 8

meiosis

Answer 8

type of cell division that gives rise to genetic variation and its role is to produce a haploid gamete cell.

• randomly ruses during fertillizatoin to form a zygote

Question 9

chromatin

Answer 9

uncodensed strands of DNA

Question 10

prophase 1

Answer 10

chromatin begins to condense and shorten forming chromosomes

nuclear envelope breaks down

spindles are made by centrioles

Question 11

metaphase I

Answer 11

chromosomes are pushed to the centre of the cell by spindle fibres and line up in homologous pairs

Question 12

Anaphase I

Answer 12

spindle fibres contact and shorten and move the chromosomes to opposite poles of the cell so one chromosome from each pair is at either end

Question 13

telophase I

Answer 13

2 nuclear envelopes form around each set of chromosomes

Question 14

cytokinesis

Answer 14

the cytoplasm divides to form 2 cells

Question 15

independent assortment

Answer 15

during metaphase 1:
order of chromosomes line up in their pairs is ranom.

• combinations of chromosomes going into the daughter cells is random

Question 16

crossing over

Answer 16

prophase 1:
- homologous chromosomes swap portions of their chromatids
- results in mixing of parental genetic info in offspring
- creates new allele combinations

Question 17

bivalent

Answer 17

structure formed by homologous chromosomes formed during crossing over

Question 18

what is a gene linkage

Answer 18

occurs when two or more genes are located close together on the same chromosome and are inherited together, this reduced independent assortment

Question 19

how does gene linkage affect genetic variation

Answer 19

• reduces genetic variation
  genes do not randomly assort during meiosis

Question 20

what are the 2 types of gene linkage

Answer 20

autosomal linkage
sex linkage

Question 21

autosomal linkage

Answer 21

genes are located on autosomes (non-sex chromosomes)

Question 22

sex linkage

Answer 22

genes are located on sex chromosomes

Question 23

how does crossing over affect linked genes

Answer 23

can separate linked genes, creating recombinants, but the likelihood depends on the distance between genes

Question 24

what is a recombinant genotype

Answer 24

arises when crossing over occurs between linked genes, producing new allele combinations different from parental types

Question 25

how can you tell if two genes are linked

Answer 25

is a 9:3:3:1 ratio in a dihybrid cross occurs

Question 26

What is the significance of recombination frequency?

Answer 26

The recombination frequency (%) indicates how close genes are on a chromosome. A higher recombination frequency means genes are further apart, while a lower frequency means genes are closer together