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A2 Biology > The origins of genetic variation > Flashcards

The origins of genetic variation Flashcards

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1
Q

Genotype

A

All the genes and alleles an organism has

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2
Q

Phenotype

A

Alleles that are expressed as a characteristic

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3
Q

Allele

A

A version of the same gene

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4
Q

Locus

A

Position of a gene

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5
Q

Homozygous

A

2 is the same alleles

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6
Q

Heterozygous

A

2 different alleles

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7
Q

Dominant

A

Alleles that are expressed

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8
Q

Recessive

A

Only expressed with 2 alleles present and without dominant present

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9
Q

Co dominant

A

2 equally dominant alleles

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10
Q

Multiple alleles

A

More than 2 alleles for the same trait

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11
Q

Gene

A

A sequence of bases on a DNA molecule coding for a sequence of amino acids on a polypeptide chain

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12
Q

Monohybrid inheritance

A

Study of the inheritance of one characteristic

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13
Q

Monohybrid inheritance: phenotypic ratio of F2 generation

A

3:1 dominant: recessive

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14
Q

Monohybrid with codominant alleles phenotypic ratio

A

1:2:1 with the 2 being both traits expressed

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15
Q

Law of segregation

A

Characteristics of a diploid organism are determined by pairs of alleles only one of which is transferred to a gamete

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16
Q

What is a test cross used for

A

Used to determine whether an organism showing the dominant characteristic is homozygous or heterozygous

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17
Q

How to perform a test cross

A

Cross with a homozygous recessive. If offspring show the recessive trait the parent must be heterozygous

18
Q

Cystic fibrosis

A

Recessive allele of a gene on chromosome 7. Normally codes for membrane protein production- CF thick mucus is produced in lungs and pancreas

19
Q

Huntington’s disease- why does this dominant allele survive in the population?

A

Delayed penetrance- symptoms don’t start until later in lire when person has most likely reproduced and passed on allele already

20
Q

Male and female heterosomes

A

Female- XX male- XY

21
Q

Genes located on heterosomes are

A

Sex linked

22
Q

Y linked diseases

A

Rare as there is little room on the chromosome

23
Q

Can males be carriers of X linked disease?

A

No but they can have the condition

24
Q

Why is X linkage more common?

A

X chromosome is larger
Part of it doesn’t have a homologous section of the Y chromosome so only one allele of a gene is present- it is always expressed

25
Q

Dihybrid inheritance

A

2 characteristics that are controlled by different genes at different loci

26
Q

Dihybrid F2 generation phenotypic ratio

A

9:3:3:1

27
Q

Genes and the environment

A

Genotype and environment result in phenotype

28
Q

Polygenic inheritance

A

Phenotype trait controlled by more than one gene

29
Q

Linkage

A

Genes that are closely located on the same chromosome tend to be inherited together unless crossing over separates them

30
Q

In crosses where linkage is happening a large proportion of the offspring are..

A

Of the parental genotype

Could expect a 3:1 ratio if genes are linked in dihybrid because they are inherited as one

31
Q

Types of selection

A

Distriptive
Stabilising
Directional

32
Q

What is a gene pool

A

Total information from all the genes and alleles of the breeding individuals in a population at a particular time

33
Q

What is happening if there is a constant change in allele frequency in a population

A

The population is evolving because the proportion of organisms in the population carrying a particular allele

34
Q

Allele frequency

A

Number of different alleles for the same trait

35
Q

Genetic drift

A

Random changes in allele frequency

36
Q

Effect of genetic drift in a large population

A

Little effect and allele frequency remains stable

37
Q

Effect of genetic drift on a small population

A

Large impact

38
Q

Population bottlenecks

A

Occurs when a genetically diverse population is drastically reduced by a non selective event eg volcano

Total genetic diversity of survivors likely to be much lower- this will be maintained even as population re establishes

39
Q

The founder effect

A

When a new population is founded from a subset of the original population eg migration of an island

40
Q

What does the hardy Weinberg assume

A

The population is large
Has random mating
Is experiencing no selection
Has no mutation emigration or immigration

41
Q

What are the equations for hardy Weinberg

A 
p+q = 1
p2+2pq+q2= 1

A2 Biology (19 decks)

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