8 Mitosis and Meiosis

Question 1

Mitosis Overview

Answer 1

Produces chromosomal and genetically identical diploid cells from parental diploid cells (typically in somatic cells)

Question 2

Cells with DNA damage arrest G1

Answer 2

Cellular senescence

Question 3

Hayflick limit

Answer 3

theoretical limit to the number of times a cell may divide until the telomere becomes so short that division is inhibited —> as cells divide the telomeres on the end of the chromosome get smaller

Question 4

Animal vs Plant cytokinesis

Answer 4

Animal - contractile ring creates cleavage furrow

Plant - vesicles fuse to form central plate

Question 5

Meiosis Overview

Answer 5

Produces cells (gametes) with haploid sets from diploid cells, typically reproductive cells

Creates genetic diversity —> random orientation of bivalents - independent segregation / assortment and the recombination of sister chromosomes

Question 6

Transmission of chromosomes between generations

Answer 6

Meiosis produces haploid gametes based on the segregation of a diploid set of chromosomes

Question 7

Generation of genetic diversity - recombination at pachytene

Answer 7

Once synapsed together in Prophase 1, the non-sister chromatids from each homologue can undergo recombination to form a hybrid, or recombinant chromatid consisting of a mixture of the parental chromatids and their alleles

Question 8

Generation of genetic diversity - random orientation of bivalents

Answer 8

Basis of Mendels - principle of independent segregation and principle of independent assortment

Synapses chromosomes (bivalents) align randomly of metaphase place and each daughter receives only 1 dopy of each himilogouse chromosome

Each daughter cell then enters prophase II, chromosomes condense and nucleur envelope breaks down and spindle apparatus form, no synapses or crossing over of homologous chromosomes since only 1 copy present so sister chromosomes no longer identical - more ways to align

Question 9

Because of ROB

Answer 9

A gamete in the son has a 1/2 chance of receiving the ‘grand’ maternal or paternal chromosomes

Possible combinations of just parental combinations (2^23)

Question 10

Meiotic error involving segregation of chromosomes

Answer 10

Non-disjunction

Aneuploidy - results in gametes with abnormal numbers (haploid is not exactly half of the diploid)

Question 11

Monosomy

Answer 11

loss of a chromosome (rare + not compatible with normal development) / shortens life span

Question 12

Trisomy

Answer 12

Gain of a chromosome (eg. Down’s syndrome)

Question 13

Gene segregation in meiosis - whats the principle based on

Answer 13

based on the behaviour of the chromosomes during meiosis

Question 14

Mendels method and analysis

Answer 14

1. Used monohybrid crosses - crosses 2 plants that differ by a single train / character
2. Use discontinuous traits which have distinct phenotypes
3. Use pure breeding
4. Able to identify and characteristics the first fillal - from the 1st generation
5. And the 2nd fillall generation

Question 15

In Monohybrid crosses, hybrid F1 seed indistinguishable from one

Answer 15

Dominant trait-the trait of the antagonistic pair seen in the F1.

Recessive trait- the trait of the antagonistic pair not seen in F1: (is masked by the dominant trait).

Reciprocal crosses showed that the parent which contributed to the dominant or recessive form did not matter.

Question 16

Testing the phenotype of different genetic strains

Answer 16

How to distinguish YY from Yy pure and hybrid pea - by test crossing - dross the strain in question with a pure breeding recessive strain

Question 17

Molecular basis of dominance - Mendel

Answer 17

Mendel chose to breed pairs of antagonistic phenotypic traits, contant, but mutually exclusive (alternative) traits, he studied phenotypic traits that are controlled by one gene, whos alleles showed complete dominate or recessiveness to eachother

Question 18

A trait can be controlled by a single…

Answer 18

Gene but its alleles show codominance (F1 phenotype is different to both parents

Question 19

Pleiotropy

Answer 19

One gene may control several traits

When one gene can control multiple phenotypes —> in these cases, apparently unconnected phenotypes can be inherited

Question 20

Polygenic

Answer 20

Most human phenotypic traits are controlled by one gene

Question 21

Number of genes calculation

Answer 21

n(n+1)/2

N - number of alleles

Question 22

Dominance series

Answer 22

When there are multiple allees for a gene, we can use pair-wise crosses to determine relationships —> see which allele is dominant for each pair to establish dominance series