Inheritance

Question 1

why does meiosis take place?

Answer 1

create unique gametes + ensures all organisms have the correct number of chromosomes

Question 2

how many cells produced from meiosis?

Answer 2

4 genetically different daughter cells

Question 3

what happens during anaphase 2?

Answer 3

chromosomes are pulled to opposite poles, forming 4 groups of chromosomes that have 1/2 the number of original diploid

Question 4

what is independent assortment?

Answer 4

the production of different combinations of alleles in dauvghter cells, as a result of the random alignment of bivalents on the equator of the spingle in metaphse I of meiosis.

Question 5

what is polyploidy

Question 6

What is autosomal linkage?

Answer 6

the prescene of 2 genes on the same autosome so that they tend to be inherited together and do not assort independently

Question 7

Mendels law of segregation

Question 8

What is epistasis?

Answer 8

it is when one gene may effect the expression of another gene at a different loci
e.g. allele G = coloured feathers allele g = no colour, but even if have allele G, if there is allele F there is no coloured feather. the presence of allele F controls the expression of allele G

Question 9

what is the chiasma?

Answer 9

position on a chromatid where crossing over of non-sister chromatids of homologous chromosomes occurs

Question 10

what is a gamete?

Answer 10

a sex cell: sperm and egg

Question 11

Define haploid and diploid.

Answer 11

diploid = 2 complete sets of chromosomes, 2n
haploid = 1 complete set of chromosomes, n

Question 12

What is a zygote?

Answer 12

a cell formed at fertilisation, at the fusion of the nuclei of 2 gametes, diploid 2n

Question 13

What are homologous chromosomes?

Answer 13

two chromosomes that carry the same genes in the same positions/loci

Question 14

What is fertilisation?

Answer 14

the fusing of the nuclei of 2 gametes, to form a zygote

Question 15

What is a gene?

Answer 15

a section of DNA on a chromosome which codes for a specific protein or polypeptide.

Question 16

What happens in prophase I?

5 things

Answer 16

chromosomes condense and become visible; arrange in homologous pairs = forms bivalents; can have crossing over occurring, w/ chiasma ; centrioles migrate to opposite ends of the call to form spindle fibres made from microtubules; nuclear envelope breaks down; nucleolus disappears

Question 17

What happens in metaphase I?

Answer 17

spindle fibres attach to the centromeres of the homologues pairs of chromosomes

Question 18

What does the chiasmata do?

Answer 18

the 2 homologous chromosomes together in the bivalent are attached to each other through the chiasma. helps hold the homologous chromosomes in the bivalent in meiosis.

Question 19

What is crossing over?

Answer 19

the exchange of alleles between non-sister chromatids of homologous chromosomes (part of a chromatid on one homologous chromosome is broken and rejoined on another chromatid from the other homologous chromosome)

Question 20

What happens in anaphase I?

Answer 20

bivalent pulled apart, 1 chromosome to each pole; centromeres remain in tact holding 2 chromatids from each chromosome together; pulled by microtubules

Question 21

What happens in telophase I?

Answer 21

spindle fibres break down; nuclear envelope forms around each set of homologous chromosomes; nucleolus reforms

Question 22

What happens in meosis I?

Answer 22

a reduction division -> went from diploid to haploid

Question 23

What is a reduction division?

Answer 23

nuclear division that results in the reduction in chromosome number

Question 24

What follows telophase I?

Answer 24

cytokinesis, forms 2 cells

Question 25

How does meiosis cause genetic variation?

Answer 25

1. random assortment
2. crossing over
3. random fertilisation

Question 26

What happens in prophase II?

Answer 26

centrioles migrate to opposite ends of the call to form spindle fibres made from microtubules; nuclear envelope breaks down; nucleolus disappears

Question 27

What happens in metaphase II?

Answer 27

chromosomes line up along the equator; spindle fibres attached to centromeres

Question 28

What happens in anaphase II?

Answer 28

centromeres divide; chromatids pulled to opposite poles by microtubules

Question 29

What is the final result of telophase II?

Answer 29

4 genetically different daughter cells

Question 30

How does crossing over create genetic variation?

Answer 30

by producing random different combinations of alleles on each chromatid. so the 4 daughter cells recieive one chromatid each, and the alleles on them will be different to original. 4 different gametes.

Question 31

How does independent assortment result in genetic variation?

Answer 31

the bivalents will align randomly along the equator in metaphse I. their orientation is completely random and the orientation of 1 bivalent will not influence another. So the mix of alleles that each gamete recieves is random and different.

Question 32

genotype vs. phenotype?

Answer 32

genotype = the alleles possessed
phenotype = the feature observed

Question 33

what are codominant alleles?

Answer 33

when both codomiant alleles are present in the genotype, they are both also in the phenotype - they are both expressed

Question 34

How do you do a test cross?

Answer 34

test with homozygous recessive to determine if organism is homozygous or heterozygous

Question 35

what is a sex linked gene?

Answer 35

a gene found on a sex chromosome that is not found on the other sex chromosome

Question 36

what is a carrier?

Answer 36

individual who possessed a particular allele in its geneotype, but it is not present in its phenotype (it is not expressed) due to being masked by a dominant allele, but the allele can be passed down to its offspring

• a heterozygote for a recessive characteristic

Question 37

What increases the chances of autosomal linkage?

Answer 37

if the 2 genes are very close to one another on the chromatid otherwise could be separated during crossing over in prophase I