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Semester 1 - Molecule, Genes and Disease > MGD Session 4 Inheritance of Genes > Flashcards

MGD Session 4 Inheritance of Genes Flashcards

1
Q

What enzymes are involved in the process of DNA replication?

A

DNA polymerase, DNA helicase and primase

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2
Q

What reaction does DNA polymerase catalyse, and give description of main reactants and products

Name four dNTPs

A

DNA polymerase catalyses the reaction (dNMP)n + dNTP  (dNMP)n+1 + PPi
(dNMP)n = DNA chain, n number of nucleotide
dNTP = any or all nucleotides, represented by N
PPi = Inorganic phosphate released

deoxyadenosine triphosphate (dATP), deoxyguanosine triphosphate (dGTP), deoxycytidine triphosphate (dCTP), deoxythymidine triphosphate (dTTP)

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3
Q

What provides the energy for the DNA polymerase reaction?

A

reaction driven by phosphate hydrolysis. Two phsophates lost from dNTP, which provides energy for polymerisation.

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4
Q

What are the three steps of DNA replication?

A

Initiation, Elongation and Termination

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5
Q

What occurs in the first step of DNA replication?

A

Point of origin determined, which differs depending on sequence.
Helicase unravels the DNA double helix
Primase adds primer to leading strand – kick starts reaction

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6
Q

Why is primase necessary to start the DNA polymerase chain reaction?

A

because DNA polymerase can only extend from 3’ ends of pre-existing chains to 5’

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7
Q

Why can DNA polymerase only extend from 3’-5’ and not vice versa?

A

Because of the shape of its active site

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8
Q

What group is attached to the 5’ carbon in a nucleotide?

A

Phosphate, 3’ is OH

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9
Q

What occurs in elongation?

A

Leading strand is replicated from 5’ –> 3’ as normal. However the lagging strand is replicated discontinuously in Okazaki fragments. These fragments are then joined by DNA ligase from OH group to Phosphate group covalently.

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10
Q

Why are Okazaki fragments formed?

A

DNA polymerase only works in 5’-3’ direction. Has to go “backwards” when forming lag strand, so discontinuous. Polymerase works a little bit at a time, moving to different sections once helicase opened up more DNA. insufficent time for continous replication on lag strand, so discontinuous,

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11
Q

What are the four sections of cell division?

A

G1 (cell growth), Synthesis (DNA replication), G2 (production of proteins necesary for division) and Mitosis

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12
Q

How many mitotic rounds during development?

A

50

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13
Q

What type of cells divide by mitosis?

A

Somatic

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14
Q

Where is the checkpoint in the cell cycle? What is its purpose?

Also, what happens in G1

A

At the start of g1, goes to g0 and causes cell cycle arrest.

Cellular contents, exculding the chromosomes, are duplicated

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15
Q

What must a cell do before it can physically divide?

A

Duplicate each of the 46 chromosomes during S phase

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16
Q

What is formed when a chromosone divides?

A

two identical sister chromatids that are touching in a structure called the centromere.

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17
Q

At what stage in cell cycle is DNA duplication checked and repaired?

A

G2

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18
Q

What happens in prophase?

A

Chromosones condense
Nuclear membrane disappearing
Spindle fibres appear

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19
Q

What happens in prometaphase?

A

Spindle fibres attach to chromosones

Chromosones condense

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20
Q

What happens in metaphase?

A

Chromosones align

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21
Q

What happens in Anaphase?

A

Centromeres divide

Sister chromatids move to opposite poles

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22
Q

What happens in Telophase?

A

Cleavage occurs
Nuclear membrane reforms
Chromosones condense
Spindle fibres disappear

23
Q

What are the two types of meiosis?

A

Spermatogeneis and Oogenesis

24
Q

How does meiosis create genetic diversity?

A

independent assortment of chromosomes (during meiosis I) and crossing-over.

25
Q

How does the process of meiosis differ from the process of mitosis?

A

In meiosis I, rather than the chromosomes lining up along the equator and the chromatids splitting apart like in mitosis, the chromosomes (duplicated from S phase) line up with their homologous pairs. This is when crossing over occurs:

26
Q

How many chromosomes in a gamete?

A

n (2n being standard), so known as haploid.

27
Q

What is the length of spermatogenesis?

A

48 days

28
Q

What is the length of oogenesis?

A

12-50 years

29
Q

Define genotype

A

The genetic make-up of an individual (either as a whole or one specific genetic locus)

30
Q

Define phenotype

A

All observable characteristics of an individual or the expressed trait as a result of the genetic make-up of one (or more) specific genetic locus (loci).

31
Q

Give five environmental factors which affect both phenotype and genotype

A 
Radiation
Mutagens
Chemicals that can affect cell growth
Diet
Life-style
32
Q

Define gene

A

A unit of heredity; a length of DNA on a chromosome that contains the code for a protein

33
Q

Define allele

A

An alternative form of a gene; each individual has two alleles for every gene, which can either be the same or different. Many different alleles in population.

34
Q

What is autosomal inheritance?

A

When the gene in question is located on an autosome (not a sex chromosome)

35
Q

What is the usual type of genotype for autosomal dominant person?

A

Heterozygous, rarely found in homozygous state as aborts fetus.

36
Q

Name a genetic disease which is autosomal dominant

A

Familial hypercholesterolemia

37
Q

If two heterozygote carriers of an autosomal recessive allele have a child, what is the chance it will be affected?

A

25%

38
Q

Name a genetic disease which is autosomal recessive

A

Cystic fibrosis, Albinism

39
Q

What is sex linked inheritance?

A

When the gene in question is located on a sex chromosome

40
Q

Give example of x-linked recessive disease

A

Haemophilla, Duchenne muscular dystrophy

41
Q

What is Y linked inheritance?

A

when the gene in question is located on the Y-chromosome and inherited directly from father to son.

42
Q

Homozygous

A

two alleles of a gene are the same

43
Q

Heterozygous

A

two alleles of a gene are different

44
Q

Hemizygous

A

Only one allele of a gene on the X chromosone (males only)

45
Q

Dominance

A

A phenotypic trait is dominant when it occurs in both homo and heterozygotes.

46
Q

Recessive

A

A phenotypic trait is recessive when it occurs only in homozygotes.

47
Q

Co-dominance

A

When both alleles are expressed in the phenotype of heterozygotes
E.g. AB Blood type

48
Q

Complementation

A

More than one gene is responsible for phenotype.
Therefore a child of two recessive parents can be unaffected if parents have different defective genes (inherits healthy genes)
E.g. Albinism
Three enzymes responsible for expression of trait

49
Q

What are linked genes?

A

Two genes close together on the same chromosome, will not show independent assortment.

50
Q

How can linked alleles be separated during mitosis?

A

By the process of crossing over and recombination

51
Q

What is recombination frequency dependent on?

A

distance between genes.

52
Q

Genes close together are…

A

tightly linked

53
Q

What does 1 map unit equal?

A

1% recombination

54
Q

When is genetic mapping more accurate?

A

When genes are close together

Semester 1 - Molecule, Genes and Disease (9 decks)

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