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AQA A-Level Biology > Chapter 17 - Inherited Change > Flashcards

Chapter 17 - Inherited Change Flashcards

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1
Q

What is the genotype of an organism?

A

All the alleles possessed by an organism

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2
Q

What is the phenotype of an organism?

A

Observable characteristics

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3
Q

What two factors contribute to the phenotype?

A

Genetics and environment

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4
Q

What is a gene?

A

Length of DNA, codes for polypeptide

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5
Q

What is the locus?

A

Position of gene on DNA strand

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6
Q

What is an allele?

A

Different forms of genes

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7
Q

What are codominant alleles?

A

Both contribute to phenotype

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8
Q

What are multiple alleles?

A

More than two alleles

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9
Q

What is pure breeding?

A

Organisms have two of the same alleles for a gene

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10
Q

What is a ratio?

A

A proportion

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11
Q

Why are the predicted results rarely the same as the observed results?

A

Only a prediction
Chance
Small sample

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12
Q

What is dihybrid inheritance?

A

Looking at how two genes on different chromosomes are inherited

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13
Q

How do you work out a dihybrid cross?

A

Do the same as a normal cross but include both genes

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14
Q

Which genotypes result in blood group A?

A

IA, IA or IA, IO

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15
Q

Which genotypes result in blood group B?

A

IB, IB or IB, IO

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16
Q

Which genotypes result in blood group AB?

A

IA, IB

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17
Q

Which genotypes result in blood group O?

A

IO, IO

18
Q

What is autosomal linkage?

A

Two or more genes are carried on the same autosome

19
Q

What impact does autosomal linkage have on a genetic cross?

A

Rather than having AB, ab, Ab, aB, you only have AB and ab because the two are linked

20
Q

What is epistasis?

A

One allele affects or masks the expression of another

21
Q

Explain epistasis in mice

A

Gene A (black bands) is affected by the expression of B (production of melanin)
bb means no melanin and an albino mouse
B means melanin is produced
If A is also present, there is a black-banded mouse
If a is also present, there is a black mouse

22
Q

What does the Chi-squared test do?

A

Test the null hypothesis

23
Q

What is the null hypothesis?

A

There will be no statistically significant difference between our expected and observed values

24
Q

What requirements does the Chi-squared test have?

A

Large sample size
Discrete categories
Raw counts, not percentages

25
Q

Formula for Chi-squared

A

https://www.statisticshowto.datasciencecentral.com/wp-content/uploads/2013/09/chi-square-formula.jpg

26
Q

What are the degrees of freedom?

A

One less than the number of categories

27
Q

If the probability that the data is due to chance is bigger than 5%, what do we do?

A

Accept the null hypothesis - the deviation is insignificant

28
Q

If the probability that the data is due to chance is less than 5%, what do we do?

A

Reject the null hypothesis - the deviation is significant

29
Q

Why will characteristics that are controlled by recessive alleles on the non-homologous section of the X chromosome appear more frequently in males?

A

There is no homologous section on the Y chromosome that may contain the dominant allele

30
Q

Example of X linked disease?

A

Haemophilia

31
Q

Where must males get their Y chromosome from?

A

Their father

32
Q

What is the law of independent assortment?

A

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

33
Q

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

A

By using a very large, representative sample

34
Q

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

A

Due to statistical error

35
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.

36
Q

Which sex chromosomes do females have?

A

XX

37
Q

Which sex chromosomes do males have?

A

XY

38
Q

How many different types of gamete do males produce?

A

2, one X and one Y

39
Q

What are sex-linked genes?

A

Any gene carried on wither the X or Y chromosome

40
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

AQA A-Level Biology (22 decks)

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