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MEO & HTC Biology A-Level > 3.7.1 Inheritance > Flashcards

3.7.1 Inheritance Flashcards

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1
Q

What is a genotype?

A

The genetic make up on an organism. It describes ALL the alleles that an organism has.

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2
Q

What is an allele?

A

A different version of the same gene

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3
Q

What is a gene?

A

Short section of DNA made up of nucleotide bases, which codes for a specific order of amino acids which makes a protein.

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4
Q

What is a phenotype?

A

Observable characteristics due to environment and genetic makeup

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5
Q

What is a homologous pair?

A

A pair of chromosomes - maternal and paternal. Also known as a bivalent

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6
Q

What is a recessive allele?

A

An allele whereby you need 2 copies of it (homozygous) to express that characteristic. Its not expressed if the dominant allele is present.

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7
Q

What is a dominant allele?

A

You only need ONE copy of this allele to express this characterisitic

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8
Q

Homozygous dominant means?

A

Two dominant alleles present (in the genotype)

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9
Q

Homozygous recessive means?

A

Two recessive alleles present (in the genotype)

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10
Q

Heterozygous means?

A

One recessive and one dominant allele present (in the genotype)

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11
Q

A codominant allele is?

A

Where both alleles contribute/expressed in the phenotype

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12
Q

What are multiple alleles?

A

Where you have more than two alleles for a particular gene

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13
Q

In a diploid organism (human) 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 - halves

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15
Q

Characteristics are determined by your allele combinations, how many alleles for each characteristics end up in the gamete?

A

1

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16
Q

Pure breeding plants are said to be

A

Homozygous

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17
Q

If there are 30 boys and 15 girls what is the ratio?

A

2:1

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18
Q

Why are actual ratios observed often not exactly the same as theoretical ratios in genetics?

A

Because fertilisation of gametes occurs by chance - each time a gamete is fertilised, it is an independent event of what has gone before it. Also, can be due to crossing over

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19
Q

How can you try and get theoretical ratios to match observed/actual ratios?

A

Increase sample size so its more representative

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20
Q

If you were to perform a statistical test on Mendelian genetics and you where looking at observed and expected ratios - what test would you do and why?

A

Chi Squared - because you are comparing observed and expected values and determining if there is a statistical difference

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21
Q

Suppose you obtained a chi squared value of 5 and the critical value was 5.99 (2dof) - what can you conclude?

A

Because the chi squared value is SMALLER than the critical value - you accept the null hypothesis and there is greater than a 5% probability that the difference in the results are due to chance. There is no significant difference.

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22
Q

Suppose you obtained a chi squared value of 8 and the critical value was 5.99 (2dof) - what can you conclude?

A

Because the chi squared value is LARGER than the critical value - you reject the null hypothesis and there is less than a 5% probability that the difference in the results are due to chance. There is a significant difference.

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23
Q

What is the difference between monohybrid inheritance and dihybrid inheritance?

A

Monohybrid is the inheritance of a SINGLE gene, dihybrid is the inheritance of TWO genes (that are located on different chromosomes)

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24
Q

Give an examples of a characteristic that involves multiple alleles

A

Blood groups - IA, IB and IO

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25
Q

Identify the chromosomes that determine sex

A

Sex Chromosomes - X and Y

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26
Q

Female sex chromosomes are

A

XX

27
Q

Male Sex Chromosomes are

A

XY

28
Q

Which sex determines the sex of the child?

A

Males - as females always pass on a X in their gametes.

29
Q

What are the criteria must be met to perform a chi squared test?

A

sample size is large (20+), data falls into catergories (green, yellow), compare experimental observations with theoretical ones (expected)

30
Q

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

A

Null hypothesis - this states that there is ‘no significant difference’….

31
Q

What is are autosomes?

A

The 22 pairs of chromosomes (not the sex chromosomes)

32
Q

What is meant by autosomal linkage?

A

This is the situation where two (or more) genes are carried on the SAME chromosome

33
Q

For autosomal linkage genetic crosses, what do we have to assume?

A

That there is no crossing over, therefore all the genes remain together during meiosis

34
Q

What is epistasis?

A

This is when the allele of one genes affects or masks the expression of another allele in the phenotype.

35
Q

If the ratio of 9:3:3:1 is not achieved when the individuals of the F1 generation are crossed what does this suggest about inheritance?

A

It is NOT your typical dihybrid cross and there is some other explanation - e.g. epistasis, linkage

36
Q

locus is

A

position on a chromsome

37
Q

a carrier is

A

a person carrying an allele not expressed in the phenotype

38
Q

what does diploid mean?

A

having 2 sets of chromosomes (pairs)

39
Q

what does haploid mean?

A

having 1 set of each chromosome

40
Q

dominant alleles are represented by using…

A

a capital letter

41
Q

recessive alleles are represented by using …

A

lower case letter

42
Q

monohybrid inheritance looks at..

A

the inheritance of a characteristic controlled by a single gene

43
Q

In blood groups which allele is recessive?

A

O

44
Q

In blood groups which alleles are codominant?

A

A and B

45
Q

A person with an A and a B allele for blood group would have what blood type?

A

AB

46
Q

A person who inherits a B allele off one parent and an O allele off another would have what blood type?

A

B

47
Q

dihybrid inheritance looks at

A

the inheritance of 2 genes located on separate chromosomes

48
Q

In a monohybrid cross what phenotypic ratios do you get in the F2 generation?

A

3:1

49
Q

In a dihybrid cross what phenotypic ratios do you get in the F2 generation?

A

9:3:3:1

50
Q

In a codominant cross what phenotypic ratios do you get in the F2 generation?

A

1:2:1

51
Q

Sometimes you do not get expected phenotypic ratios because of …

A

sex linkage, autosomal linkage, epistasis, small sample size

52
Q

Name a sex linked condition

A

haemophilia, colour blindness

53
Q

A characteristic is said to be sex linked when..

A

its carried on the sex chromosome

54
Q

How can you tell from looking at the family tree if a condition is sex linked?

A

males will only be affected

55
Q

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

A

only have 1 copy of X - so a recessive trait would be expressed

56
Q

How are the X and Y chromosomes different?

A

X bigger (more genes), Y smaller (fewer genes)
no homologous portion on the Y

57
Q

During autosomal linkage what happens?

A

genes are inherited together

58
Q

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

A

if crossing over during meiosis 1 has occurred

59
Q

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

A

because cross over is less likely to split them up

60
Q

what does the null hypothesis always start with?

A

there is no significant difference….

61
Q

If 2 genes are said to be linked what does this mean?

A

they are on the same chromosome

62
Q

a gene pool is

A

ll the alleles (of all of the genes) in a population

63
Q

what is meant by the genome

A

all the DNA in a cell/organism

MEO & HTC Biology A-Level (6 decks)

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