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Genetics > Review 1 > Flashcards

Review 1 Flashcards

1
Q

How do we count chromosomes?

A

by the number of centromeres present

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2
Q

At the beginning of MI, how many chromosomes does the cell contain?

A

46 chromosomes

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3
Q

At the beginning of MI, how many chromatids does the cell contain?

A

92 chromatids

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4
Q

At the end of MI, how many chromosomes does the cell contain?

A

23 chromosomes

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5
Q

At the end of MI, how many chromatids does the cell contain?

A

46 chromatid

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6
Q

At the end of MII, how many chromosomes does the cell contain?

A

23 chromosomes

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7
Q

At the end of MII, how many chomatids does the cell contain?

A

23 chromatids

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8
Q

Immediately after fertilization, how many chromosomes does the zygote contain?

A 
Zygote: 
46 chromosomes (46 chromatids) 
Sperm/Egg:
23 chromosomes (23 chromatids)
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9
Q

Immediately after fertilization, how many chromatids does the zygote contain?

A

46

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10
Q

The zygote prepares to divide. Immediately before the first mitotic division, the cell
contains how many chromosomes?

A

46 chromosomes

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11
Q

The zygote prepares to divide. Immediately before the first mitotic division, the cell
contains how many chromatids?

A

92 chromatids

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12
Q

There are now 2 cells in the embryo. How many chromosomes does each cell contain?

A

46 chromosomes

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13
Q

There are now 2 cells in the embryo. How many chromatids does each cell contain?

A

46 chromatids

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14
Q

How many chromosomes do humans have?

A

46 chromosomes

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15
Q

What are names of each type of chromosome?

- what are there characteristics?

A

1) Metacentric:
Centrome in middle

2) Submetacentric:
Centromere off center with arms of different lengths

3) Acrocentric
centromere near one end has stalk and satellite

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16
Q

How many arms does a chromosome have?

A

2 arms: short (p for petite) and long (q)

-Q is on the bottom half and P is on the top half

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17
Q

What are the phases of Interphase?

A

G1- interval b/w mitosis and replication: Preparing to replicate
-10-12 hours

S- DNA replication occurs
(6-8 hours)

G2: Interval b/w S and mitosis
(repair occurs)
(2-4hrs )

M: Mitosis

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18
Q

What are the 5 Cell cycle checkpoints?

A
  1. After G1 phase
  2. Middle of S phase
  3. After G2 phase
  4. Middle of M phase
  5. After M phase/cell division
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19
Q

What happens at the checkpoint in between G1 and S phase?

A

Ensure integrity of the genome

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20
Q

What happens at the checkpoint during G2 phase?

A

Block of mitosis entry until DNA replication is complete and DNA damage is repaired

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21
Q

What happens after the checkpoint after the M phase?

A

Block of chromosomes segregation until chromosomes are correctly aligned on the mitotic spindle

22
Q

What happens at PROPHASE?

A

● Chromosomes condense

● Mitotic spindle/centrosomes begin to form

23
Q

What happens at Prometaphase?

A

● Nuclear membrane disappears

24
Q

What happens at Metaphase?

A

● Chromosomes fully condensed
● Chromosomes line up on metaphase plate
● Spindle fibers begin to contract

25
Q

What happens during Anaphase?

A

● Centromeres divide into two

● Spindle fibers pull chromatids toward opposite sides of the cell (centromere first)

26
Q

What happens during Telophase?

A

● Cytokinesis (form two identical daughter cells)
● Two nuclear membranes form
● Spindle fibers disappear
● Chromosomes decondense and return to interphase

27
Q

What is Meiosis I?

A

Reduction Division
-46–>23; 2n–>1n
Diploid-> haploid

***Homologues separate

28
Q

What is Meiosis II

A

Identical to mitosis in somatic cells except only 23 chromosomes present

-sister chromatids separate

29
Q

At the beginning of meiosis 1, a human cell contains ____________chromosomes, or ___________ chromatids (the same number as during mitosis)

A
  • 46

- 92

30
Q

In meiosis II, a cell containing ________ chromatids undergoes division in 2 cells, each with _________ chromosomes.

A
  • 46

- 23

31
Q

At the end of meiosis II is 4 cells, each with _______ chromosomes and ______ chromatid.

A
  • 23

- 23

32
Q

Immediately after fertilization, what is the chromosomal complement of the zygote?

A 
diploid 2n ( paired chromosome one from each parent) 
-46
33
Q

Tell me about male gamatogenesis

A

1) Starts at puberty
2) Continues throughout life
3) One germ cell produces 4 sperms(primary spermatogonium)
4) Think about autosomal dominant disorders with older dad (yes 35!)

34
Q

Tell me about female gamatogenesis

Think about chromosomal nondisjunction within older moms

A

1) Starts in embryonic life (3 months)
2) Primary oocyte remains suspended in prophase of MI until puberty
3) Follicle matures, oocyte proceeds to complete MI producing secondary oocte & asp polar body
4) After ovulation each oocyte continues to metaphase of MII
5) MII only completed upon fertilization resulting in fertilized ovum and 2nd polar body

**One egg and two polar bodies after fertilization. Without fertilization, one egg and one polar body.

35
Q

Average size of a gene?

A

○ 14,000 base pairs

36
Q

What is 1 cM equivalent to?

A

cM= 1 Mb= 1,000,000 bp DNA

1cM=1% recombination

37
Q

What is DNA→ DNA called? DNA → RNA? RNA→ protein?

A

○ DNA → DNA: Replication
○ DNA → RNA: Transcription
○ RNA → Protein: Translation

38
Q

Tell me about genetic code?
-How many codons total?

  • How many amino acids only have 1 codon?
  • How many stop codons?
  • Is the code the same for nucleic DNA and mitochondrial DNA?
A

64

  • only 2;
    1) Tryptophan (Trp) UGG
    2) Methionine (Met) AUG - Start Codon
  • 3 stop codons: UAA, UAG & UGA
  • No, it uses non-universal codon
39
Q

Autosomal Recessive Rules?

A

1) Appears in both sexes w/ equal frequency
2) Tends to “skip” generations
3) Affected offspring born to unaffected parents
4) When both parents are heterozygous, approx. 1/4 kids affected
5) Appears more frequently in consanguine marriages

40
Q

Autosomal Dominant Rules?

A

1) Appears in both sexes w/ equal frequency
2) BOTH sexes “transmit” the trait to kids
3) NO SKIPPING GENERATIONS
4) Affected kids have affected parents unless they have a new mutation
5) When one parent is affected, (heterozygous) and the other is not, 1/2 of kids affected

41
Q

X-linked Dominant Rules?

A

1) Both males and females are affected, but more often females
2) Doesn’t skip generations
3) Affected sons must have affected mother
4) Affected daughters have affected mother or father
5) Affected father will pass trait to all their daughters
6) Affected heterozygous moms will pass trait on to half sons and half daughters

42
Q

X-linked Recessive Rules?

A

1) More males than females affected
2) Affected sons are born to unaffected mothers, thus trait SKIPS GENERATIONS
3) 1/2 of the carrier mothers’ sons will be affected
4) never passed from father to son
5) all daughters of affected fathers are carriers

43
Q

How can a female have an X-linked recessive disorder

A
  • If she inherits BOTH faulty bad X’s
  • If mom is a carrier & dad is affected = Females will be 25% affected and 25% carriers
  • If mom is NOT a carrier and dad is affected then ALL daughters are carriers (50%)
OR
Skewed X inactivation 
-Affected father & carrier mother thru assortative mating 
-Consanguinity
-Turner Syndrome (45, X)
44
Q

Prader-Willi and Angelman syndromes are the best examples of what in humans?

A

Non-Mendilian Inheritance, Atypical Pattern of Inheritance.

They’re also BEST examples of GENETIC IMPRINTING : Differential modification and expression of alleles of a gene depending on the sex of the parent of origin.
45
Q

What is the most common mechanism that causes PWS? and AS?

A

PWS:

  • Deletion on father’s chromosome 15
  • Maternal uniparental disomy (paternal inactive)
  • **70% have deletions in 15q11q13 paternal

AS:

  • Deletion on mother’s chromosome 15
  • Paternal uniparenetal disomy (maternal inactive)
  • ***68% have deletions in 15q11q13 maternal
46
Q

What is the most efficient method for testing for Prader-Willi and Angelman syndromes?

A

○ Methylation analysis

(detects ~99% of PWS and ~78-80% of AS)

47
Q

What are the components of a PCR reaction?

A
  • DNA template
  • DNA polymerase
  • primers
  • nucleotides
  • RT-PCR (reverse transcriptase )
48
Q

Uniparental disomy has implication for which types of disorders?

A

○ Uniparental disomy - Inheritance of 2 copies of a gene or chromosome from 1 parent.

■ Implications for RECESSIVE disorders and IMPRINTING disorders
● First described in a child with cystic fibrosis; only the mother was a carrier
● very important for PWS and AS

49
Q

What makes up one cycle of PCR?

A

1) DENATURE the DNA sequence to render it single stranded
2) ANNEAL
3) Primer EXTENSION

● Use taq polymerase at 72C b/c its thermophillic (heat loving)
■ Repeated 28-35 times
■ Each cycle is about 5 minutes
■ Results in an exponential increase in the amount of the desired sequence
(i.e. amplification)

50
Q

What are Mendel’s Laws?

A

1) Law of Segregation
- Members of each pair of alleles separate when gametes are formed. A gamete will receive one allele or the other

2) Law of independent assortment
2 or more pairs of alleles segregate independently of one another during gamete formation

Genetics (4 decks)

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