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Cell, Organisms And Systems > Linkage and Meiosis - Genetics 3 > Flashcards

Linkage and Meiosis - Genetics 3 Flashcards

1
Q

Meiosis

A

type of cell division that occurs in sexually reproducing organisms to create gametes (haploid)

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2
Q

Haploid

A

Cells with one set of chromosomes (23)

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3
Q

Diploid

A

Cells with 2 sets of chromosomes that are copies of eachother

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4
Q

Alleles in a zygote

A

2 alleles of each gene (one maternal and one paternal)

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5
Q

How does meiosis produce 2 haploid daughter cells?

A

One round of DNA replication and two rounds of chromosome segregation

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6
Q

Chromosome Segregation

A

Distribution of chromosomes/chromatids into daughter cells.

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7
Q

First round of chromosome segregation in meiosis

A

Anaphase 1 - homologous chromosomes separate (pairs of chromosomes)

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8
Q

Second round of chromosome segregation in meiosis

A

Anaphase II - sister chromatids separate (one chromosome into its 2 arms) by the centromere

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9
Q

Haploid Daughter Cells

A

Cells with half the chromosome complement.

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10
Q

Independent Assortment

A

Random distribution of chromosomes during meiosis depending on how the line up during metaphase I and II

Difference between number of segregations and if the daughter cells are genetically identical to the parent cell in mitosis vs meiosis
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11
Q

Meiosis I

A

First meiotic division, specialized chromosome segregation.

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12
Q

Difference between segregation in mitosis and meiosis 1

A

In mitosis kinetochores (proteins) pull apart sister chromotids by the centromere with spindle fibres whereas in meiosis one homologous pairs ar epulled apart

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13
Q

Key steps for meiosis I to occur

A
  • Pairing of homologous chromosomes
  • Synapsis
  • Crossing over
  • Mono-orientation of kinetochore
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14
Q

What needs to happen in meiosis I for the homologous chromosomes to be separated?

A

The cell needs to be able to recognise homologous chromosomes in order for pairing to occur. Once they pairs find each other they must stay together before division

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15
Q

Synapsis

A

Pairing of homologous chromosomes during prophase I of meiosis.

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16
Q

Crossing Over

A

Exchange of genetic material between homologous chromosomes.

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17
Q

Synaptonemal Complex

A

Structure facilitating synapsis of homologous chromosomes. Made of highly conserved proteins that link together and is well orchestrated.

Electron micrograph of Synaptonemal Complex. The more dense fields (lateral elements on both sides) have homologous proteins wound around them

The crossing of colours (homologous chromosomes) shows strand break and repair from another chromosome = CROSSING OVER

18
Q

What holds sister chromatids together?

A

Chohesin. Most need to be lost in order for the chromatids to later be separated

19
Q

Separase

A

Enzyme that cleaves a part of the chromosome arms, so chohesin is no longer keeping them together. Some remains in the central part, keeping the sister chromatids together at the centrophere and next to the kinetochore.

Action of active separase in meiosis one
20
Q

Crossover Recombination

A

Creation of novel allele combinations in gametes during meiosis one (recombinanat chromatids)

Recombination of genes close to each other on the same chromosome is rare

21
Q

Meiosis products are parental types

A

A result of no crossing over between the genes (recombination). Results are in expected ratios

22
Q

Meiosis products are recombinant (and parental)

A

Crossing over breaks linkage of genes on chromosomes, creating recombinant genes where some are from paternal and some maternal.

23
Q

Recombination and linkage tells us that…

A

Genes are on the same chromosome. It doesn’t tell us how close they are

24
Q

Genetic Linkage

A

Tendency of genes on the same chromosome to be inherited together. Distorts mandelian ratios

25
Q

Phenotypes meet expected ratio

A

We can make the assertion that we are looking at unlinked genes (on different chromosomes)

26
Q

Recombinant Frequency

A

Percentage of recombinant offspring from a cross.

27
Q

Calculating recombination freqency

A

Add up amount of recombinant individuals and divide by the total number of individuals

28
Q

CentiMorgan (cM)

A

A distance. Map unit for measuring genetic linkage (distance between genes on a chromosome. It = recombination frequency as a %

29
Q

What would happen to recombination frequency and genetic map distance if there were 2 crossover events between the 2 genes?

A

A more diverse recombination frequency. Lots of different outcomes of phenotypes.

30
Q

Why is there a max recombination frequency?

A

More than 50 = the genes are on different chromosomes. Around 49 suggests the two genes are at either end of the chromosome. The genes are unlinked.

31
Q

What would happen to recombination frequency and genetic map distance if the 2 genes were closer together on the same chromosome?

A

Recombination frequency would decrease as crossing over separating the genes is less likely to occur (the genes are close together on the chromosome)

32
Q

Unlinked genes

A

Genes located on different chromosomes or very far apart on the same chromosome

33
Q

Mendelian Ratios

A

Expected ratios of offspring phenotypes from genetic crosses.

34
Q

Two Crossover Events

A

Can maintain parental genotype despite recombination.

35
Q

Linkage-Based Diagnostic Test

A

Test determining parental origin of chromosome regions for several embryones to know if offspring is affected, a carrier or unaffected.

36
Q

Monogenic Disease Screening

A

Testing for single-gene disorders using linkage.

37
Q

Gametes

A

Haploid cells involved in fertilization.

38
Q

Alleles

A

Different versions of a gene.

39
Q

Heterozygous

A

Having two different alleles for a gene.

40
Q

Homozygous

A

Having identical alleles for a gene.

Cell, Organisms And Systems (16 decks)

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