T 4 Flashcards

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1
Q

Genetic variation in meiosis

A

Prophase 1
crossing over between homologous chromosomes
exchange of alleles between them
forms different sequences of ( maternal and paternal) alleles on each chromosome

Metaphase 1
Homologous pairs align @ equator in a random order, independent
making it random as to which homologous chromosome from each pair will end up in the daughter cell
Producing different combinations of alleles in each daughter cell

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2
Q

What are the key events of Meiosis 1?

A

Separation of homologous pairs

first chromosomes form homologous pairs
crossing over
independent segregation
both introduce genetic variation

2n-n, daughter cells are haploid

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3
Q

Key events of meiosis 2

A

separation of chromatids

n-n
produces haploid, genetically different gametes 4 of them

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4
Q

Importance of meiosis

A

produces haploid gametes
diploid post fertilisation
so chromosome number remains constant from one gen to next

introduces genetic variation ind seg and cross ov

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5
Q

chromosome non-disjunction

A

homologous chromosomes fail to separate in A1 or chromatids in A2
one gamete with 1 extra 1 with 1 less
1 less- dies
1 more- survives but infertile

occurs spontaneously
case of some genetic diseases

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6
Q

number of possible different combinations of chromosomes in daughter cells after meiosis

A

2^n

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7
Q

number of different possible combinations of homologous chromosomes following fertilisation

A

(2^n)^2

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8
Q

Life cycles in n

A

n-2n fertilisation
2n-2n mitosis
2n-n meiosis

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9
Q

Prokaryotic vs eukaryotic DNA

A

Eu (us)
long, linear, assorted with histone proteins, tightly coiled into chromosomes

Pro
short, circular, not associated with histone proteins

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10
Q

Define a homologous pair of chromosomes

A

pair of chromosomes exactly the same size and carrying the same genes but having different alleles

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11
Q

Role of courtship behaviour

A

INCREASE CHANCE OF SUCCESSFUL MATING

allows recognition of members of the same species, as behaviour is species specific

attraction of a mate

sign of sexual maturity

stimulates the realise of gametes

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12
Q

Measuring genetic diversity

A

compare:
amino acid base sequences of common proteins as coded by mRNA-DNA
base sequence of DNA
frequency of observed characteristics, as different characteristics are coded for by different alleles

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13
Q

limitations of observable characteristics as a measure of genetic diversity

A

characteristics can be polygenetic, coded for by more than one gene
characteristics can be altered by the environment, not reflect genetic differences

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14
Q

Conservation techniques applied to farming

A

crop rotation using nitrogen fixing crops
maintenance of hedge rows
reduce use of pesticides/ herbicides
use of natural rather than artificial fertilisers

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15
Q

How to take a representative sample

A

use random sapling techniques to eliminate bias

divide area you wish to sample up into a grid, give each grid square co-ordinates
generate numbers randomly to generate a set of coordinates
sample at the intersection of each coronate using quadrants

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16
Q

Comparing the base sequence of genes provides more evolutionary information than comparing the structure of proteins
Explain why.

A

Reference to base triplets / triplet code / more bases than amino acids / longer base sequence than amino acid sequence;

Different (base) triplets code for same amino acids = 2 marks;
Degeneracy of triplet code = 2 marks

Introns / non-coding DNA / degeneracy of code / more than one code for each amino acid;