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A Level Biology > ✅17 - Inherited Change > Flashcards

✅17 - Inherited Change Flashcards

1
Q

What is a genotype?

A

The genetic makeup of an organism, all the alleles that it has

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2
Q

What is a phenotype?

A

The observable or biochemical characteristics of an organism. The result of the interactions between expression of the genotype and the environment

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3
Q

What is a gene?

A

A length of DNA

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4
Q

What are alleles?

A

Different forms of genes

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5
Q

What is a locus?

A

The position of a gene on a particular DNA molecule

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6
Q

What are homologous pairs of chromosomes?

A

Pairs of chromosomes with approximately the same length, gene position and centromere location

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7
Q

What is homozygous?

A

When an individual has two of the same allele

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8
Q

What is heterozygous?

A

When an individual has two different alleles

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9
Q

What does codominant mean?

A

Where two alleles both contribute to the phenotype

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10
Q

What are multiple alleles?

A

When a gene has more than two allelic forms, of which only two may be present at the loci on an individual’s homologus chromosomes

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11
Q

What is monohybrid inheritance?

A

Inheritance of a single gene

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12
Q

What is the F1 generation?

A

First filial - two different pure breed organisms crossed to give hybrid offspring

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13
Q

What is the F2 generation?

A

Second filial - heterozygous offspring from F1 generation crossed together to produce more offspring

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14
Q

What is the law of segregation?

A

In diploid organisms, characteristics are determined by alleles that occur in pairs. Only one of each pair of alleles can be present in a single gamete.

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15
Q

Why are actual results of genetic crosses rarely the same as predicted?

A

Due to statistical error

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16
Q

How can results of genetic crosses be made to be closer to predicted ones?

A

By using a very large, representative sample

17
Q

What is dihybrid inheritance?

A

Two characteristics, determined by two different genes located on different chromosomes are inherited

18
Q

What is the law of independent assortment?

A

Each member of a pair of alleles may combine randomly with either of another pair

19
Q

What is an example of codominance?

A

The snapdragon plant, which has one allele for an ezyme that catalyses the formation of red pigment and one which produces no pigment - red and white. However, the two colour combine to give pink flowers

20
Q

What is an example of multiple alleles?

A

Blood group

21
Q

Which sex chromosomes do females have?

A

XX

22
Q

Which sex chromosomes do males have?

A

XY

23
Q

How many different types of gamete do males produce?

A

2, one X and one Y

24
Q

What are sex-linked genes?

A

Any gene carried on wither the X or Y chromosome

25
Q

Why can some genes be more prevalent in males than females?

A

The X chromosome is much longer than the Y, so more most of the X chromosome, there is no homologous equivalent and those recessive characteristics on the X chromosome will be more frequent in males

26
Q

What is an X-linked genetic disorder?

A

A disorder caused by a defective gene on the X crhomosome

27
Q

What is an example of an X-linked genetic disorder?

A

Haemophillia

28
Q

What are autosomes?

A

Any chromosome which is not a sex chromosome

29
Q

What is autosomal linkage?

A

When two or more genes are carried on the same autosome

30
Q

Why do linked genes remain together when passed onto offspring?

A

Because, assuming that there is no crossing over, they do not segregate in accordance with Mendel’s law of independent assortment

31
Q

What is epistasis?

A

When the allele of one gene affects or masks the expression of another in the phenotype

32
Q

What is an example of epistasis?

A

In mice, where several genes determine coat colour

33
Q

How does epistasis in mice work?

A

Gene A controls distribution of black pigment and whether they are banded or not. The dominant allele of A leads to hairs with black bands, which recessive a produces uniform black hairs.
Gene B controls expression of A. Dominant B leads to production of the pigment while recessive b leads to no pigment

34
Q

Which statistical test is used for genetics?

A

Chi Squared

A Level Biology (22 decks)

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