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AQA A Level Biology > 3.7.1 Inheritance > Flashcards

3.7.1 Inheritance Flashcards

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1
Q

What is the genotype?

A

All the alleles that an organism has

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2
Q

What is the phenotype?

A

The observable or biochemical characteristics of an organism

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3
Q

What is a gene?

A

A length of DNA which is a sequence of nucleotide bases

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4
Q

What is an allele?

A

One of the different forms of a gene

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5
Q

What is the locus?

A

The position of a gene on a particular DNA molecule

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6
Q

What are homologous chromosomes?

A

Chromosomes in pairs with the same gene loci

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7
Q

What are homozygous alleles?

A

When both alleles are the same

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8
Q

What are heterozygous alleles?

A

When the alleles are different

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9
Q

What is a dominant allele?

A

One that is expressed

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10
Q

What is a recessive allele?

A

One that is not expressed

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11
Q

What is it called when a homozygous organism has two dominant alleles?

A

Homozygous dominant

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12
Q

What is it called when a homozygous organism has two recessive alleles?

A

Homozygous recessive

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13
Q

Define codominant alleles

A

When both alleles contribute to the phenotype. This can either be a blend of features or when both features are represented

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14
Q

What is it called when an organism is said to have multiple alleles?

A

When a gene has more than two allelic forms

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15
Q

What is a Punnett square?

A

A cross diagram used to show the genes of genetic offspring

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16
Q

What are pure breeding strains?

A

When alleles are the same

17
Q

What is the generation called if it is a cross between two pure breeding parents?

A

First filial or F1 generation

18
Q

What is the generation called when an F1 generation is crossed with another F1 generation?

A

Second filial or F2 generation

19
Q

What is dihybrid inheritance?

A

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

20
Q

How many chromosomes do humans have?

A

23 pairs

21
Q

Define sex-linked

A

When a gene is carried on the X or Y sex chromosome

22
Q

Which sex chromosome is longer?

A

X
So most of the X chromosome don’t have an equivalent homologous portion
Those non-homologous chromosomes have no pairing so will always be expressed

23
Q

What is an X-linked genetic disorder?

A

A disorder caused by a defective gene on the X chromosome

24
Q

How is a sex linked allele represented?

A

X or Y to the power of (letter respresenting the allele)

25
Q

Why do males always inherit an X-linked genetic disorder from their mothers?

A

They have to get their Y chromosome from their father so the X chromosome must be from the mother

26
Q

What are the sex chromosomes for males and females?

A

XX for females

XY for males

27
Q

What is a carrier?

A

A person who has an allele of a disease without displaying the physical symptoms

28
Q

What is a pedigree chart?

A

A chart which shows the inheritance of sex-linked characters in a family
A male is represented as a square
A male is represented by a circle
Shading indicates the presence of a character in the phenotype

29
Q

What are autosomes?

A

The chromosomes which aren’t sex chromosomes

30
Q

Define linked genes

A

When two genes occur on the same chromosome

31
Q

What forms a linkage group?

A

All the genes on a single chromosome

32
Q

What is the name of the situation where two or more genes are carried on the same autosome?

A

Autosomal linkage

33
Q

Draw a diagram of non-linked genes

A

See card

34
Q

Draw a diagram of linked genes?

A

See card

35
Q

Does independent selection affect autosomal linkage?

A

No

36
Q

How do you complete the chi squared test?

A

Columns: category, observed number (O) , expected number (E) , O - E, (O - E)2, (O - E)2 / E
X2 = Sum of: (O - E)2 / E

37
Q

How do you evaluate the value calculated in the chi squared test?

A

If your calculated value is less than the degree of freedom, accept the null hypothesis that there is a significant difference between your observed and expected results
If the value is larger than the degree of freedom, there is epistasis or linkage of the alleles

38
Q

What is epistasis?

A

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

39
Q

How do you use the word epistatic?

A

If one gene locus prevents the expression of a second gene, the first locus is epistatic to the second and the second is hypostatic to the first

AQA A Level Biology (51 decks)

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