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Ib biology > Topic 10 > Flashcards

Topic 10 Flashcards

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1
Q

When do chromosomes replicate?

A

During interphase

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2
Q

What phase of interphase does DNA replication occur?

A

S phase

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3
Q

What is produced from DNA replication?

A

Two sister chromatids that are held together by a centromere

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4
Q

Which meiosis do sister chromatids separate?

A

Meiosis 2

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4
Q

Which meiosis do sister chromatids separate?

A

Meiosis 2

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5
Q

Outline the stages of meiosis

A 
P1
M1
A1
T1
P2
M2
A2
T2
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6
Q

What happens during prophase 1?

A

Chromosomes condense, nuclear membrane dissolves, homologous chromosomes form bivalents, crossing over occurs

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7
Q

What happens during metapahse 1?

A

M-I: Spindle fibres from opposing centrosomes connect to bivalents (at centromeres) and align them along the middle of the cell

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8
Q

What happens during Anaphase 1?

A

A-I: Spindle fibres contract and split the bivalent, homologous chromosomes move to opposite poles of the cell

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9
Q

What happens during Teleophase 1?

A

Chromosomes decondense, nuclear membrane may reform, cell divides (cytokinesis) to form two haploid daughter cells

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10
Q

What happens during Prophase 2?

A

Chromosomes condense, nuclear membrane dissolves, centrosomes move to opposite poles (perpendicular to before)

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11
Q

What happens during Metaphase 2?

A

M-II: Spindle fibres from opposing centrosomes attach to chromosomes (at centromere) and align them along the cell equator

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12
Q

What happens during Anaphase 2?

A

A-II: Spindle fibres contract and separate the sister chromatids, chromatids (now called chromosomes) move to opposite poles

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13
Q

What happens during teleophase 2?

A

T-II: Chromosomes decondense, nuclear membrane reforms, cells divide (cytokinesis) to form four haploid daughter cells

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14
Q

Why is there an independent assortment of genes?

A

Due to random orientation of pairs of homologus chromosomes

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15
Q

What is the orientation of each pair of chromosome?

A

The orientation of each homologous pair is random and is not affected by the orientation of any other homologous pair

16
Q

When will independent assortment not occur?

A

When genes are located on the same chromosome ( linked genes)

17
Q

What chromatids do a chiasmata form between?

A

Non sister chromatids

18
Q

Synapsis

A
  • During prophase I of meiosis, homologous chromosomes become connected in a process known as synapsis
  • The connected homologues are known as a bivalent
  • While autosomes always undergo synapsis during meiosis, sex chromosomes often remain unpaired
19
Q

Chiasmata

A

While in synapsis, non-sister chromatids may break and recombine with their homologous partner (crossing over)

These non-sister chromatids remain physically connected at these points of exchange – regions called chiasmata

Chiasmata (singular = chiasma) hold the homologous chromosomes together as a bivalent until anaphase I

Chiasmata formation between non-sister chromatids can result in the exchange of alleles

20
Q

Draw a diagram to show chiasmata formation

A
21
Q

What does crossing over produce?

A

-Crossing over produces new combinations of alleles on the chromosomes of the haploid cells

22
Q

What is crossing over?

A

The exchange of DNA between non sister chromatids

23
Q

What are recombinant chromosomes

A

The chromosomes that consist of genetic material of both homologues

24
Q

What are unlinked genes

A

pairs of alleles are inherited independently of one another if their gene loci are on separate chromosomes

25
Q

What does the independent segregation of unlinked genes lead to?

A

greater number of potential gamete combinations, as well as a greater variety of possible phenotypes

26
Q

What method can you use to work out the gamete combination in a dihybrid cross?

A

FOIL method

27
Q

What is a gene pool?

A

All the genes and alleles within an interbreeding population

28
Q

What does evolution require?

A

There is a change in allele frequency with time in populations

29
Q

What can cause the allele frequency within a gene pool to change?

A

Mutation: A random change in the genetic composition of an organism due to changes in the DNA base sequence
Gene flow: The movement of alleles into, or out of, a population as a result of immigration or emigration
Sexual reproduction: Sex can introduce new gene combinations and alter allele frequencies
Genetic drift: The change in the composition of a gene pool as a result of a random event
Natural selection: The change in the composition of a gene pool as a result of differentially selective environmental pressures

30
Q

Allele frequency comparisons

A
  • Allele frequencies represent the prevalence of a particular allele in a population
  • Consequently, allele frequencies are either represented as a percentage or as a value from 0 to 1.0
  • Changes in allele frequency can reflect either random processes (genetic drift) or differential processes (natural selection
31
Q

What are the three types of selection?

A
  • Stabilising
  • Disruptive
  • Directional

Ib biology (11 decks)

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