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Y2 Human Genetics > Transmission Genetics > Flashcards

Transmission Genetics Flashcards

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1
Q

Define Hereditary

A

The transmission of traits and characteristics from one generation to the next passed from the genes of a parent to a child.

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2
Q

How many pairs of chromosomes do humans have?

A

23

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3
Q

Define polygenic trait

A

A trait caused by the accumulation of many different gene codes.

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4
Q

Define Pleiotropic genes

A

A single gene controlling how multiple traits will be expressed.

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5
Q

Define mendelian Trait

A

Traits decided by a single gene.

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6
Q

What are somatic cells and describe their chromosomal count

A

Somatic cells are autosomal, non-sex cells and are usually diploid which means they have two sets of chromosomes, one from each parent.

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7
Q

What are gametes and describe their chromosomal count

A

Gametes are sex cells and are haploid meaning they only contain one set of chromosomes.

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8
Q

What are Polyploid cells

A

These cells have more than 2 chromosome sets in each cell

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9
Q

What is dominance in terms of genetics?

A

The relationship between alleles where one allele can completely mask the functioning of another (recessive) allele.

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10
Q

Define homozygous

A

An individual inherits the same alleles for a particular gene from both parents.

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11
Q

Define heterozygous

A

An individual inherits different alleles for a particular gene from each parent.

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12
Q

Define phenotype

A

The set of observable characteristics of an individual from the interaction of the genotype with the environment.

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13
Q

Define genotype

A

The genetic constitution of an individual organism

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14
Q

What is a Pleiotropic gene ?

A

A gene that has an effect on more than one trait

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15
Q

What type of characteristic is one who’s determined by polygenic genes?

A

Polygenic characteristic

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16
Q

What type of genes control most human characteristics?

A

Polygenic genes

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17
Q

What experiment did Gregor Mendel use to prove his points about genetics?

A

The pea experiment

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18
Q

When did Gregor Mendel publish his work ?

A

1865

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19
Q

When was Gregor Mendel work recognised and who by?

A

1906 (after Mendel had died) by William Batemen.

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20
Q

Who coined the term “genetics”?

A

William Bateman

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21
Q

What is ‘The blending hypothesis’?

A

The idea that the genetic material from two parents blends together.

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22
Q

What is ‘The particulate hypothesis’?

A

The idea that parents pass on discrete heritable units known as genes.

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23
Q

What hypothesis did Mendel put forward?

A

The particulate hypothesis

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24
Q

What is meant by the term ‘character’ in genetics?

A

A heritable feature that varies among individuals is called a ‘character’.

25
Q

What is meant by the term ‘trait’ in genetics?

A

Each variant for a character (such as purple or white flower colour).

26
Q

Why did Mendel choose to carry out his experiments on pea plants?

A

Peas are easy to grow and cross-fertilise.

They produce large numbers of offspring to investigate.

The peas had only 2 possible variants which made the experiment easy in terms of counting the results as the peas were either one character or another - no blend.

27
Q

What are pure breeds?

A

This means that if you had a true breeding plant with wrinkled seeds and allowed it to self-pollinate, it will always produce offspring with wrinkled seeds.

28
Q

How many traits did Mendel study at a time?

A

1

29
Q

Did Mendel study any sex-influenced traits?

A

No

30
Q

By what method did Mendel mate two contrasting, true-breeding variants?

A

Hybridisation

31
Q

In Mendel’s experiment, what was the first generation after the parental generation?

A

F1 - first filial generation.

32
Q

In Mendel’s experiment, how was the F2 generation produced?

A

The F1 individuals self-pollinate or cross-pollinate with other F1 hybrids to produce the F2 generation.

33
Q

What did Mendel Hypothesise?

A
  • That the heritable factor for white flowers was not lost in the F1 generation but was based when the purple flower factor was preset.
  • He also deduced that there must be two factors for each flower colour in each plant, but one factor can be masked by another.
  • The explained a 3:1 inheritance pattern.
34
Q

What are Mendel’s postulates?

A
  1. Heritable traits are determined by heritable factors, now called genes. Genes come in pairs.
  2. Genes come in different versions, now called alleles. When an organism has two different alleles of a gene, one (the dominant allele) will hide the presence of the other (the recessive allele) and determine the characteristic.
  3. During gamete production, each egg or sperm cell received just one of two allele copies present in the organism, and the copy is allocated to each gamete at random. This is the law of segregation.
  4. Genes for different traits are inherited independently of one another - this is the law of independent assortment.
35
Q

What is the law of segregation?

A

During gamete production, each egg or sperm cell received just one of two allele copies present in the organism, and the copy is allocated to each gamete at random.

36
Q

What is the law of independent assortment?

A

Genes for different traits are inherited independently of one another.

37
Q

What is the place where each gene resides on a specific chromosome known as ?

A

A locus

38
Q

What is meant by the term haplosufficiency ?

A

In a case where the genotype is heterozygous, the allele which causes one trait is sufficient for that characteristic.

39
Q

What is meant by an allele being nutant?

use Mendel’s flower colours as an example

A

The allele for white flowers doesn’t actually code for white pigment, it just doesn’t code for the functional enzyme to code for purple pigment.

40
Q

What is a mono genie disease?

A

A single pair of alleles or a single gene will be responsible for the disease.

41
Q

Give an example of a monogenic disease ?

A

Sickle cell anaemia

42
Q

What are alleles?

A

Alternative forms of a single gene

43
Q

Are homozygous organisms true breeding ?

A

Yes

44
Q

Are heterozygous organisms true breeding ?

A

No

45
Q

What is the purpose of a punnet square ?

A

To analyse genotypes and resulting phenotypes from the recombination of gametes during fertilisation.

46
Q

When is the 3:1 ratio for offspring produced in terms of a punnet square?

A

When there is a monohybrid cross.

2 heterozygous parents are crossed.

47
Q

What is meant by the 3:1 offspring ratio?

A

When two heterozygous parents are breeded, the possible offspring genotypes are homozygous dominant, heterozygous X 2 and homozygous recessive.

Of these 4 combinations, 3 will show the dominant characteristic (phenotype) and 1 will show the recessive.

48
Q

What is the purpose of a test cross in genetics?

A

Uses a punnet square approach to work out what genotype a dominantly expressing allele actually is.

Can also be used to determine parental phenotype.

49
Q

How can alleles cause genetic disorders?

A

They may code for a dysfunctional protein or not code for a protein at all.

50
Q

What is a dihybrid cross?

A

Crossing two true-breeding parents different in two characteristics.

51
Q

What is a dihybrid organism?

A

Organisms that are heterozygous at two different genetic loci.

52
Q

Why did Mendel succeed?

A

He derived postulates that have become the principles of transmission genetics.

Mendel’s law of segregation and independent assortment reflects the rules of probability.

53
Q

What is epistasis?

A

Where the alleles of one gene can mask the effects of the alleles of another gene.

54
Q

What is incomplete dominance?

A

Phenotype of the dominant allele doesn’t completely mask the recessive allele.

55
Q

What does incomplete dominance produce in offspring ?

A

Crosses between organisms with two different phenotypes produces offspring with a third phenotype that is a blending of the parental traits.

56
Q

What is Codominance?

A

Phenotypes of both alleles are expressed.

57
Q

What are the possible number of gametes in a monohybrid cross?

A

2

58
Q

What are the possible number of gametes in a dihybrid cross?

A

4 (2 x 2)

59
Q

What are the possible number of gametes in a Trihybrid cross?

A

8 (2 x 2 x 2)

Y2 Human Genetics (1 decks)

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