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1. A level master > Inheritance > Flashcards

Inheritance Flashcards

1
Q

What is a genotype?

A

Genetic make up of an organism.
ALL the alleles that an organism has.

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2
Q

What is an allele?

A

Different versions of a gene found at the same locus on a chromosome.

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3
Q

What is a gene?

A

Short section of DNA that codes for a single polypeptide

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4
Q

What is a phenotype?

A

Observable or biochemical characteristics of an organism.
Expression of the genotype and its interaction with the environment.

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5
Q

What is a homologous chromosomes

A

A pair of chromosomes matched in shape and size, which contain the same genes.
Formed when haploid gametes fuse to make zygote at fertilisation

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6
Q

Gene locus

A

Position of a gene on a chromosome

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7
Q

Homozygous

A

Two alleles at a gene locus are the same

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8
Q

Heterozygous

A

Two alleles at a gene locus are different

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9
Q

Dominant allele

A

The allele of the heterozygote that is expressed in the phenotype

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10
Q

Recessive allele

A

The allele that is only expressed when homozygous. It is not expressed when a dominant allele is present.

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11
Q

A dominant allele is …

A

expressed in the phenotype

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12
Q

What are multiple alleles?

A

There are more than two alleles for a particular gene

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13
Q

In a diploid human cell how many chromosome pairs are there?

A

23

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14
Q

In meiosis, what happens to the diploid number?

A

It becomes haploid.
It halves

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15
Q

Pure breeding plants are …

A

Homozygous

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16
Q

What is the difference between monohybrid inheritance and dihybrid inheritance?

A

Monohybrid - inheritance of a SINGLE gene
Dihybrid - inheritance of TWO genes (that are located on different chromosomes)

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17
Q

Give an example of a characteristic that involves multiple allelles

A

Blood groups

18
Q

Identify the chromosomes that determine sex

A

X and Y
In most organisms XX = female and XY = male

19
Q

When might you use a Chi squared test?

A

Sample size is large (20+)
Data falls into categories
Compare experimental observations with theoretical/expected ones.

20
Q

When performing a statistical test what must you always state before you carry out the test?

A

Null hypothesis
There is no significant difference between …. and …

21
Q

What are autosomes?

A

The chromosomes that are not the sex chromosomes. In humans there are 22 pairs of autosomes.

22
Q

What is meant by autosomal linkage?

A

Two (or more) genes are carried on the SAME chromosome

23
Q

For autosomal linkage what do we have to assume?

A

There is no crossing over
Genes remain together during meiosis

24
Q

What is epistasis?

A

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

25
Q

What phenotypic ratio would you expect for a monohydrid cross between two heterozygous individuals?

A

3:1
3 dominant : 1 recessive

26
Q

What phenotypic ratio would you expect for a dihybrid cross between two heterozygous individuals?

A

9:3:3:1

27
Q

A carrier is ….

A

A person in possession of an allele that is not expressed in the phenotype

28
Q

What phenotypic ratio would you expect for codominant cross between 2 heterozygotes?

A

1:2:1

29
Q

Sometimes you do not get expected phenotypic ratios because …

A

Small sample size
Autosomal linkage
Epistasis

30
Q

Name a sex linked condition

A

Haemophilia
Colour blindness

31
Q

A characteristic is sex linked when …

A

Its is carried on the sex chromosomes

32
Q

How can you tell from a pedigree chart if a condition is sex linked.

A

Males will only be affected

33
Q

Why are males more likely to express recessive traits of sex-linked conditions?

A

Only have 1 copy of X chromosome
No second allele to mask a recessive one

34
Q

How are X and Y chromosomes different to each other?

A

X is bigger/contains more genes
Y is smaller/contains fewer genes

35
Q

When might genes that are present on the same chromosome NOT be inherited together?

A

Crossing over in meiosis I (prophase)

36
Q

The closer together 2 genes are the more closely linked they are - why?

A

Crossing over is less likely to split them up

37
Q

If two genes are said to be linked what does this mean?

A

They are on the same chromosome

38
Q

What is meant by codominant alleles?

A

Two dominant allleles that both contribute to the phenotype, by showing a blend of both characteristics or the characteristics appearing together.

39
Q

A woman has the blood group O. Give her genotype.

A

XX Io Io

40
Q

A male has blood group AB. Give his genotype

A

XY IA IB

1. A level master (39 decks)

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