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MGD > Session 4 > Flashcards

Session 4 Flashcards

1
Q

At which stage of the cell cycle does cell content replication occur?

A

Growth phase 1 (G1)

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2
Q

At which stage of the cell cycle does DNA replication occur?

A

Synthesis phase (S phase)

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3
Q

What direction does the DNA chain grow in DNA replication?

A

5’ to 3’

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4
Q

What drives the DNA replication reaction?

A

Pyrophosphate hydrolysis

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5
Q

How is DNA replication initiated in prokaryotes.

A

Origin of replication is recognised.
DNA polymerase and other specific proteins are recruited.
Reaction kicked off by primase because DNA polymerase can only extend a 3’ end.

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6
Q

On which strand of DNA is replication continuous?

A

Leading strand (strand where the original strand streches from 3’ to 5’)

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7
Q

On which strand of DNA is replication not continuous, what is formed instead, and why?

A

Lagging strand (strand stretching from 5’ to 3’).
Forms Okazaki fragments.
DNA polymerase can only form DNA from 5’ to 3’ so it must work backwards on this strand to form many smaller fragments of complimentary DNA.

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8
Q

How are Okazaki fragments joined?

A

Using DNA ligase.

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9
Q

What is used to unzip DNA in replication?

A

DNA helicase.

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10
Q

What is a replication fork in DNA replication?

A

The area on the DNA strand which is unwound and currently undergoing replication.

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11
Q

How is DNA replication terminated?

A

Replication starts in several places along a chromosome when 2 regions of replicating DNA meet replication stops.
The DNA strands are joined by DNA ligase where they meet.

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12
Q

What are metacentric chromosomes?

A

Chromosomes where the centromere is in the middle of the chromosome.
P and Q arms are similar lengths.

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13
Q

What are submetacentric chromosomes?

A

Chromosomes where the centromere is towards the top of the chromosome.
P arm is shorter than the Q arm.

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14
Q

What are acrocentric chromosomes?

A

Chromosomes where the centromere is very close to the top of the chromosome.
P arm is considerably shorter than the Q arm.

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15
Q

What are telocentric chromosomes?

A

The chromatid is at the top of the chromosome.
No P arm only a Q arm.
Don’t occur in humans.

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16
Q

After DNA replication does the chromosome number change? Why?

A

Chromosome number stays the same.

One replicated chromosome consists of two sister chromatids.

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17
Q

What is mitosis?

A

Cell division of somatic cells.

Produces 2 identical daughter cells with the same chromosome content as the parental cell.

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18
Q

In what order does mitosis occur?

A

Prophase, prometaphase, metaphase, anaphase, telophase, cytokinesis.

19
Q

What occurs in prophase in mitosis?

A

Spindle fibres form from a pair of centrioles.

Chromosomes appear in the nucleosome.

20
Q

What occurs in prometaphase in mitosis?

A

Spindle fibres bind to the kinetocore of each chromosome.

21
Q

What occurs in metaphase of mitosis?

A

Centrioles of spindle fibres line up at the poles of the cell and chromosomes line up along the metaphase plate along the equator of the cell.

22
Q

What occurs in anaphase of mitosis?

A

Daughter chromosomes split up from the chromosome and migrate towards the poles attached to kinetocore spindle fibres.

23
Q

What occurs in telophase of mitosis?

A

The nuclear envelope reforms and delve age furrows appear.

Spindle fibres disappear.

24
Q

What occurs in cytokinesis of cell division?

A

The cytoplasm divides so the parent cell becomes 2 daughter cells.

25
Q

What is meiosis?

A

Cell division for germ line cells.
Produces 4 non-identical cells with half the chromosome content of the parental cells.
Occurs as a round of replication followed by 2 rounds of division.

26
Q

What creates variation in meiosis and how?

A

Crossing over: bivalent forms of chromosomes line up and cross over at chiasmata to exchange portions of DNA with each other.
Random assortment: chromosomes are randomly assorted after division to produce a unique combination of chromosomes.

27
Q

What occurs in meiosis 1?

A

Cells divide to produce 2 diploid daughter cells.

Crossing over occurs so the genetic material in each daughter cell is not identical.

28
Q

What occurs in meiosis 2?

A

Daughter cells divide to create haploid gametes.

Random assortment occurs to give each gamete a unique combination of DNA.

29
Q

In spermatogenesis, how many sperm are produced from one spermatocyte.

A

4, all daughter cells go on to produce 2 gametes.

30
Q

In oogenesis, how many ovum a are produced from one oocyte?

A

1, 3 polar bodies are produced from the other gamete cells.

31
Q

Why must crossing over occur?

A

If crossing over didn’t occur, meiosis couldn’t occur because all genetic material in meiosis 1 would be passed on to one daughter cell. This would produce cells in meiosis 2 with diploid chromosomes so no gametes would form.

32
Q

What is genotype?

A

The genetic makeup of an individual. Can refer to the alleles of a particular gene that are present.

33
Q

What is phenotype?

A

The observable characteristics or traits of an individual.

34
Q

Define homozygous.

A

2 alleles of a gene are the same in an individual.

35
Q

Define heterozygous.

A

2 alleles of a gene are different in an individual.

36
Q

Define hemizygous.

A

Only one allele of a gene (on the X chromosome) is present.

Only occurs in males.

37
Q

What is a dominant allele?

A

The allele of a gene that determines the phenotype.

38
Q

What is a recessive allele?

A

The non-dominant allele of a gene.

39
Q

What is co-dominance in a gene?

A

More than one allele is dominant in the gene so multiple alleles can determine the phenotype.

40
Q

In blood type, which alleles are dominant over each other?

A

A and B are both dominant over O.

Neither A or B are dominant over each other.

41
Q

What are linked genes? What do they show?

A

Genes on the same chromosome.

They show no independent assortment in meiosis.

42
Q

What are non-linked genes? What do they show?

A

Genes on different chromosomes.

They show independent assortment in meiosis.

43
Q

Which enzyme catalysts DNA replication?

A

DNA polymerase

MGD (10 decks)

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