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Biology 8.1 > Genetic information > Flashcards

Genetic information Flashcards

1
Q

What is Meiosis

A

A reduction division that occurs only in the sex organs.

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2
Q

What does meiosis do to chromosome number in cells?

A

it halves the chromosome number in the cells from diploid to haploid

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3
Q

In what two ways does meiosis introduce genetic variation?

A

1) Independent assortment (random assortment)

2) Crossing over (recombination)

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4
Q

In humans where do the 23 chromosomes in your gametes come from?

A

It’s random so could come from your maternal or paternal chromosomes

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5
Q

What does independent assortment result in?

A

It results in many new combinations of alleles and introduces considerable genetic variation.

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6
Q

When does crossing over take place?

A

During meiosis when large multi-enzyme complexes ‘cut and join’ bits of the maternal and paternal chromatids together at the chiasmata.

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7
Q

What benefits does Crossing over have and how?

A

It leads to genetic variation as many new combinations of alleles rises.

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8
Q

What is a mutation?

A

A permanent change in the DNA of an organism

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9
Q

Name two ways in which mutations can take place?

A

1) When the gametes are formed

2) During the division of somatic (body) cells

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10
Q

When do mutations sometimes have a positive effect?

A

When environmental conditions change it may make organisms better adapted for survival

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11
Q

Are all mutations cut out or repaired in the body?

A

No,some mutations are transcibed from DNA to mRNA and translated when new proteins are made.

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12
Q

What are the three main types of mutation and what are they caused by?

A

1)Point and gene mutation
Caused by miscopying of just one or small number of nucleotides. (Deletion,Insertion and Substitution)
2)Chromosomal mutations
Caused by changes within a gene in a chromosome
3)Chromosomal mutations
when an entire chromosome is either lost during meiosis or duplicated in one cell via errors.

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13
Q

Name a few sources of genetic variation in sexual reproduction?

A

Meiosis
Mutations
Random Fertilisation

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14
Q

What is a phenotype?

A

The physical and chemical charecteristics that make up the appearance of an organism

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15
Q

Name two things the phenotype is a result of?

A

1) Genotype (genetic information)

2) Environmental factors.

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16
Q

What is the difference in genotype between two individuals of a species due to?

A

1) Shuffling of genes during meiosis

2) Inheritance of genes from two different individuals in sexual reproduction

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17
Q

How many chromosomes do humans have?

A

46

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18
Q

What makes the chromosome in a homologous pair distinct?

A

The fact that they carry the same gene (except sex chromosomes)

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19
Q

How many genes do you carry for a charecteristic

A

Two

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20
Q

What is an allele?

A

Different version of the same gene

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21
Q

What is a homozygote?

A

Both the alleles coding for a particular charecteristic are identical.

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22
Q

What is a heterozygote?

A

Both the alleles codes for a different charecteristic

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23
Q

What is polygenic?

A

most traits in living organisms are determined by several interacting genes

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24
Q

Why are homozygotes refered to as ‘true breeding’?

A

All the offsprings in the future will show the same charecteristics in their phenotype.

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25
Q

Why is heterozygotes not true breeding?

A

The offspring will include homozygote dominant heterozygote reccesive and heterozygpes type + atleast two different phenotypes

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26
Q

What is a monogenetic cross?

A

When one gene is considered at a time in genetic cross

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27
Q

What does a punnett square show?

A

The potential alleles inherited from both parents and the potential offsprings that result.

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28
Q

What is F1?

A

The first generation from the monogenetic crosses

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29
Q

What is F2

A

If we cross individuals from the F1 generation it is known as F2.

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30
Q

Why are the theoretical ratios predicted by genetic cross never precise?

A

1) Chance plays a role in reproduction
2) Some offsprings die before they can be sampled
3) Inefficient samplling techniques

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31
Q

Why did Mendel decide to investigate peas?

A

He could see that they had characteristics that varied in a clear-cut way.
They were easy to grow
He could control which plant pollinated each other

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32
Q

What is the first law that Mendel presented?

A

The law of segregation

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33
Q

What was the law of segregation a result of?

A

A result of his work with monohybrid crosses.

34
Q

What does the law of segregation state?

A

One unit or allele for each trait is inherited from each parent to give a total of two alleles for each trait.

35
Q

When does segregation of alleles in each pair take place?

A

When the gametes are formed

36
Q

What is the second law Mendel presented?

A

The law of independent assortment

37
Q

What does the law of independent assortment state?

A

Those different traits are inherited independently from independently of each other

38
Q

What do multiple alleles mean?

A

There are more than two possible variants

39
Q

Give one clear example of multiple alleles

A

human blood type ABO

40
Q

What are the three possible alleles in ABO

A

A, B and O

41
Q

What do the different alleles code for?

A

The presence or absense of antigens on the surface of the erythrocytes

42
Q

What antigens do each code for:
Ia
Io
Ib

A

1) Antigen A
2) No antigen
3) Antigen B

43
Q

which one of the following is recessive:
Ia
Io
Ib

A

Io is the only recessive one

the rest are dominant

44
Q

Ia and Ib are codominant. What does this mean?

A

Both alleles are expressed and produce their proteins , which act together without mixing.

45
Q

What is the key feature of codominance?

A

There is no blending in the phenotype

46
Q

What are digenetic crosses?

A

Breeding experiments involving the inheritance of two pairs of constrasting charecteristics at the same time

47
Q

What is a parental phenotype?

A

They are the same as the original parents

48
Q

what is a recombinant phenotype?

A

They are different from the original parents

49
Q

Which one of mendels laws does dihybrid crosses follow and how?

A

The law of independant assortment

The two sets of alleles are on different chromosomes,seperated into the gametes independantly of each other

50
Q

In dihybrid crosses,why might the ratios sometimes not be what you expected?

A

.Small sample size
.Experimental error
.Process is random,so unexpected may happen
.Unexpected ratios can mean the gene being examined are both on the same chromosome

51
Q

What is the difference between a hypothesis and null hypothesis

A

Hypothesis is the theory we are hoping to prove whereas null hypothesis is the theory we are hoping to disprove

52
Q

What is the chi-squared test?

A

A relatively simple statistical method that is used to establish whether any difference between the observed and expected results are significant or due to chance

53
Q

What is the formulae for the chi-squared test?

A

x2=< (o-E)2
———-
< E

54
Q

What does everything in the chi-squared test stand for

A

O=observed result
E=expected result
< =sum of

55
Q

Is knowing the chi-squared enough?

A

No, you need to know the number of degree of freedom in a system

56
Q

What is the number of degree of freedom in a system

A

The spread of the data

it is always one less than the number of categories in a the data

57
Q

What is the probability of 0.05 used as?

A

cut off point to show the difference between our predicted and observed results

58
Q

What does it mean if your probability is greater than 0.05

A

There is no difference between what we expected and what we observed so we can accept the null hypothesis

59
Q

What does it mean if your probability is less than 0.05

A

There was a statistically significant difference between the observed number and the expected number so we will reject the null hypothesis

60
Q

What is a gene linkage?

A

When the genes for two characteristics are found on the same chromosome and are close together so they are linked and inherited as a single unit

61
Q

What happens when genes are rarely linked?

A

Recombination events during meiosis rarely occur in the gametes

62
Q

What is less likely to happen to genes that are very close together?

A

They are less likely to be split during the crossing over stage of meiosis than genes that are further apart

63
Q

How do you know when gene linkage is involved in dihybrid crossing

A

When the typical 9:3:3:1 ratio doesn’t occur

64
Q

What is the formulae for working out the crossover value

A

crossover value = number of recombinant offspring X100
—————————————————–
total number of offspring

65
Q

What will result in low crossover values

A

Closely linked genes producing only small number of recombinant offspring

66
Q

What will result in high crossover value

A

Genes that are further apart produce larger number of recombinants

67
Q

What does the chromosome in diploid organisms occur as?

A

homologous pairs

68
Q

What two hormones do females carry and what is the name used to describe it?

A

XX chromosomes

homogametic

69
Q

What two hormones do males carry and what is the name used to describe it?

A

XY chromosomes

heterogametic

70
Q

In humans how many pairs of the following do we have:
autosomes
sex cells

A

22 pairs of autosomes

1 pair of sex cells

71
Q

Where is the SRY gene carried?

A

in the Y chromosome

72
Q

How many base pairs do the follwing have and which one is bigger:
X
Y

A

150million
23million
The X chromosome is bigger

73
Q

Genes that are carried on the X chromosome are sex-linked. What does this mean

A

Any reccessive or mutant alleles passed on the X chromosome from a mother to her son will be expressed in the phenotype as there is no corresponding allele on the homologous Y chromosome

74
Q

What is albinism?

A

A condition in which the natural melanin pigment of the skin, eyes and hair does not form

75
Q

What is the most common form to albinism due to

Is this type of albinism dominant or reccesive

A

A mutant allele that prevents the formation of a normal enzyme in the cell.The enzyme tyrosinase, which is often active in melanocytes, is not formed correctly and the reaction to make melanine cannot take place.
Reccesive

76
Q

What is human color vision a result of?

A

Three different types of light sensative cells called cones found in the retina of the eye

77
Q

Where are the genes for human colour vision found

A

In the X chromosme

78
Q

What is the cause of red-green blindness?

What sex is it more common for

A

Reccesive mutation in the X chromosome

more common in men than women

79
Q

What is Haemophilia?

A

A sex linked trait in which one of the proteins needed for the blood is missing

80
Q

What is Haemophilia A

A

Sex linked condition that involves the lack of clotting factor VII

81
Q

What can an untreated male haemophiliac lead to

A

If a slight injury takes place it could lead to death due to excessive bleeding
even excercise can lead to internal bleeding of joints

Biology 8.1 (1 decks)

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