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AQA A Level Biology > Inheritance > Flashcards

Inheritance Flashcards

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1
Q

Define diploid

A

An organism with a pair of homologous chromosomes, it has 2 alleles of each gene

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2
Q

Define gene

A

A sequence of DNA that codes for a certain protein

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3
Q

Define allele

A

A variation of a gene

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4
Q

Define genotype

A

The combination of alleles that an organism has

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5
Q

Define phenotype

A

The physical expression of the genotype and its interactions with the environment

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6
Q

What is a dominant allele?

A

An allele always expressed in the phenotype

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7
Q

What is a recessive allele?

A

An allele only expressed when it is homozygous

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8
Q

What is a codominant allele?

A

When both alleles are expressed in the phenotype as an intermediate

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9
Q

Define homozygous

A

Both alleles are the same

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10
Q

Define heterozygous

A

Both alleles are different

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11
Q

Define locus

A

The location/position of a gene on a chromosome, the alleles of a gene always have the same locus

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12
Q

What is monohybrid inheritance?

A

Inheritance of a characteristic controlled by a single gene

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13
Q

What will be the F2 Phenotypic ratio of a monohybrid inheritance from a homozygous dominant male and a homozygous recessive female?

A

3 : 1Dominant : Recessive

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14
Q

What is dihybrid inheritance?

A

Inheritance of two characteristics that are controlled by separate genes

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15
Q

What will be the F1 generation be in a dyhybrid cross between a homozygous dominant and a homozygous recessive?

A

100% heterozygous

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16
Q

What will be the ratio of the F2 generation in a dyhybrid cross between a homozygous dominant and a homozygous recessive?

A

9 : 3 : 3 : 19 : Both dominant 3 : Dominant allele 1, recessive allele 23 : Dominant allele 2, recessive allele 11 : Both recessive

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17
Q

What is codominance?

A

When there are multiple alleles that are dominant and can all be expressed in the phenotype as an intermediate

18
Q

What is an example of codominance?

A

Blood group

19
Q

What will be the F1 generation of a codominant cross between two different homozygous dominant patents

A

100% heterozygous

20
Q

What will be the F2 generation phenotypic ratio of a codominant cross between two different homozygous dominant patents

A

1 : 2 : 11 : Homozygous allele 11 : Homozygous allele 22: Heterozygous

21
Q

What is epistasis?

A

An interaction between genes where the expression of one gene suppresses the expression of another

22
Q

How would you refer to two genes showing epistasis

A

gene … is epistatic to gene …

23
Q

How does epistasis effect phenotypic ratios?

A

A dihybrid cross on epistatic genes will not result in the normal phenotypic ratio

24
Q

What is the phenotypic ratio of a dihybrid cross where the epistatic gene is recessive?

A

9 : 3 : 4

25
Q

What is the phenotypic ratio of a dihybrid cross where the epistatic gene is dominant?

A

12 : 3 : 1

26
Q

What is an autosome?

A

A non-sex chromosome

27
Q

How many autosomes do humans have?

A

44

28
Q

What is an autosomal linkage?

A

It is where two genes are found on the same autosome and are therefore inherited together

29
Q

What is autosomal linkage not affected by?

A

independent segregation

30
Q

Does autosomal linkage affect the phenotypic ratios from a dihybrid cross?

A

Yes, because linked genes are inherited together they behave more like a monohybrid cross

31
Q

What does an autosomal linkage mean for offspring?

A

They are more likely to have the same genotype and phenotype as their parents

32
Q

What can affect an autosomal link?

A

Crossing over, however this is dependent on the loci of the two genes. The closer to two are and the closer the autosomal link the less likely they are to be separated during crossing over but it is not impossible

33
Q

What will be the result of the phonotypes and genotypes of offspring after an inherited autosomal link, taking crossing over into account?

A

The majority of offspring will share their parents phenotypes and genotypes however a small percentage will not because of crossing over

34
Q

Where are homologous pairs found?

A

In diploid organisms

35
Q

What are homologous pairs?

A

Same gene but different allele

36
Q

What is a sex linkage?

A

The expression of alleles located on sex chromosomes depends on the sex of the individual

37
Q

What are the sex chromosomes of a female?

A

XX

38
Q

What are the sex chromosomes of a male?

A

XY

39
Q

What is different about the X and Y chromsomes?

A
  • X chromosome is much bigger than Y- Y is missing many of the genes present on X
40
Q

What is typical of a sex linkage phenotypical ratio?

A

1 : 1Female carrier : Male sufferer

AQA A Level Biology (13 decks)

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