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Genetics > Lecture 1 > Flashcards

Lecture 1 Flashcards

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1
Q

How many base pairs are in the haploid human genome

A

3 billion in haploid, 6 billion in genome

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2
Q

How related are the genomes of 2 unrelated people

A

99.5%

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3
Q

How many chromosomes in the human

A

46 chromosomes, 23 paired in females (22 X and 1 Y chromosome in males)

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4
Q

What percent of the genes are protein-coding genes

A

2%

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5
Q

How long is DNA if stretched out from single cell

A

2 meters long

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6
Q

What is a gene

A

a basic unit of hereditary material
- A segment of DNA that produces a polypeptide chain

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7
Q

How are genes usually defined

A

commonly defined by the linkage they have to disorders (i.e. BRCA causes breast cancer)

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8
Q

Genetic information is carried in units called

A

genes

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9
Q

Diploid vs haploid cells in the human body

A

Diploid: 2 copies of genetic material (i.e most cells in the body)
haplid: cell with a single set of unpaired chromosomes (sex cells)

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10
Q

What is an allele

A

a different form of a gene
- Variation in nucleic acid sequence of genes leads to 2 different alleles

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11
Q

How many alleles can a diploid organism have

A

2 copies of the same allele or 2 different alleles

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12
Q

Homozogote vs heterozygote

A

Homozygote: 2 copies of same allele
Heterozygote: 2 different alleles

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13
Q

Comparison of genotype vs phenotype

A

Genotype: the alleles someone has (i.e. Aa)
Phenotype: visible expression of genotype (i.e. green eyes with Aa and blue eyes with aa)

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14
Q

What are polygenic and monogenic related to and waht do they mean

A

related to phenotypes
Polygenic: many genes influence a trait (most human characteristics)
Monogenic: Phenotype influenced by only 1 gene

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15
Q

What is the backbone of DNA

A

Sugar-phosphate backbone

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16
Q

Central dogma of genetics

A

DNA transcribes into RNA(transcription, DNA and RNA same language) , RNA is translated into proteins (different languages so must translate)

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17
Q

How do retroviruses work?

A

use reverse transcriptase, turn RNA to DNA (backwards)

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18
Q

What are autosomes

A

non-sex chromosomes

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19
Q

What are chromosomes made of

A

proteins and nucleic acids. Nucleic acid chain wrapped tightly around a histone protein

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20
Q

Which organelle is maternal?

A

Mitochondria- all have small circular chromosome and have multiple copies

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21
Q

What do helicases do

A

unwind the dna helix, seperate the strands

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22
Q

What does Primase do

A

build RNA primers on DNA strands to give DNA polymerase place to build new DNA strand

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23
Q

What does polymerase do

A

add base to new DNA strands. Catalyzes the covalent addition of free nucleotides to new DNA strands

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24
Q

Which enzyme do chemotherapy drugs target commonly

A

polymerase, inhibits cancerous dna transcription

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25
Q

How is DNA replication considered semiconservative?

A

Open up DNA, keep one old strand and make one new strand (2 new strands from one DNA strand since it’s split)

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26
Q

Where are covalent bonds in DNA and RNA

A

between phosphate and nucleotides

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27
Q

Functions of RNA

A

-Sending transcription messages
-Form ribosomes to synthesize proteins
-Translate from nucleic acid to amino acid sequence

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28
Q

What are amatoxins? What are they related to?

A

-Deadly inhibitors of human RNA polymerase
- Cause of death from mushroom poisoning
- Can’t make proteins we need, so we can’t transcribe the proteins we need

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29
Q

Which antibiotic inhibits RNA polymerase?

A

Rifampin

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30
Q

Is the sense or antisense strand used to make RNA transcript?

A

Antisense- made sense strand

31
Q

What 2 regions does RNA polymerase work between

A

Promotor and terminator

32
Q

Describe the process of DNA to mRNA

A

DNA is transcribed, has introns removed, exons spliced together, and is then mRNA

33
Q

What is tRNA’s relationship to mRNA

A

complementary

34
Q

What percent of mutations are replication errors vs chemical or environmental damage

A

65% are replication errors
35% are chemical or environmental damage

35
Q

Are mutations usually harmful?

A

Very few are harmful, most don’t have much effect because cells have enzymes to repair DNA

36
Q

What do RNA viruses like coronavirus rely on?

A

RNA dependent RNA polymerases to do retrovirus things (go from rna to dna)

37
Q

What is the only way we get new alleles created?

A

mutations

38
Q

What are germinal mutations vs somatic mutations

A

Germinal mutation: in sperm or egg
Somatic mutation: in somatic cell (i.e. skin cancer)

39
Q

What is a point mutation?

A

Base substitutions (Supposed to be T, puts in G instead).
Results in: transitions(purine to purine (just different letters for same amino acid)) or transversion (purine to prymidene)

40
Q

What are insertion and deletion mutatoins

A

Frameshift mutations (add or remove entire nucleic acids)

41
Q

What is a duplication mutation

A

gene or segment of DNA is copied or stuck

42
Q

What is aneuploidy

A

additional chromosomal copies or deleted copies

43
Q

Purines vs prymidines

A

Purine: A/G
Pyrimidines: T/C

44
Q

What is a strand slippage

A

one nucleotide strand forms a loop, base pair falls out of strand

45
Q

Do insertions/deletions or base substitutions occur more frequently?

A

Insertions and deletions

46
Q

What mutation leads to unequal crossing over

A

Deletions and insertions

47
Q

Describe the 3 phenotypic effects of mutations

A
  1. Missense mutation: new codon encodes different amino acid, change in amino acid sequence
  2. Nonsense mutation: New codon is stop codon
  3. Silent mutation: New codon encodes same amino acid, no change in aa sequence
48
Q

What is aneuploidy

A

one extra single chromosome (23+1 chromosome)

49
Q

What is polyploidy

A

all chromosomes have an extra pair (usually no birth)

50
Q

Describe metacentric, sub-metacentric, acrocentric, and telocentric for centromeres

A

Metacentric: centromere in middle of chromosomes
Sub-metacentric: almost at the middle
Acrocentric: to one side of the chromosomes
Telocentric: Centromere at the very end of the chromosomes

51
Q

4 different Chromosome rearrangements during replication

A

Duplication: chromosome segment duplicated
Deletion: chromosome segment deleted
Inversion: segment turned 180 degrees
Translocation: segment moved elsewhere on different chromosome

52
Q

Nonreciprocal vs reciprocal translocation

A

Nonreciprocol: Segment from one chromosome to another, no exchange back
reciprocol: two chromosomes swap (balanced)
Robertsonian: One chromosome is attached to another (considered type of balanced reciprocol)

53
Q

Common examples of robertsonian translocation

A

13 and 14,
14 and 21

54
Q

Tandem duplication vs displaced duplication vs reverse

A

Tandem: immediately adjacent duplication
Displaced: somewhere else on the same chromosome or on another chromosome
Reverse: inverted (180 degrees) duplicated

55
Q

What are ring chromosomes

A

deletion of both chromosomal arms in duplication, sticky ends form a ring.
Ring 14 is common

56
Q

How do polyploidy fetuses occur

A

when 2 sperm fertilize an egg at the same time- entire extra set of genes. Do not make it to birth

57
Q

What is nondisjunction

A

homologous chromosomes or sister chromatids fail to seperate
- Lead to aneuploidy (abnormal number) or trisomy(3 copies of given chromosome)

58
Q

What are the 4 types of aneuploidy

A

Nullisomy- loss of both chromosome pairs
monosomy: loss of 1 chromosome
trisomy: gain single chromosome
Tetrasomy: gain 2 homologous chromosomes

59
Q

Why are some chromosomes able to have viable trisomys?

A

They have a smaller number of genes per chromosome so an extra copy makes it possible, a smaller number of genes makes less of an effect (i.e. chromosome 21 has 300 genes to be duplicated instead of the 2544 genes on chromosome 1)

60
Q

What is associated with maternal age

A

aneuploidy

61
Q

What is down syndrome related to (chromosome)

A

Trisomy 21, extra 21 chromosome

62
Q

What are some of the key features of Down syndrome?

A
  • Most common chromosomal disorder
  • short neck, heart and respiratory defects, delayed or reduced mental development, increased risk of lukemia and alzheimers
63
Q

What increases risk of down syndrome

A

mother’s age/paternal age

64
Q

What gene rearrangement can cause down syndrome

A

An extra part of chromosome 21 is attached to another chromosome in the parent. When the parent reproduces, it leads to 3 chromosomes for 21 (down syndrome)
Caused by robertsonian translocation

65
Q

Edward’s syndrome pathology

A

Extra chromosome 18
1/5 born can live to 1 month
born usually with organs outside of the body

66
Q

Patau syndrome pathology

A

Extra chromosome 13
Median survival is 10 days
Low birth weight, major brain development problems

67
Q

Turner’s syndrome pathology

A

Only one X chromosome in sex chromosome (X monosomy)
- Hypogonadism, short stature, webbed neck.
- Not able to reproduce, or have menstrual cycle
1/3000 females

68
Q

Poly X syndrome pathology

A

No syndrome defined
Tall and thin women, normal intelligence (4 or more X and decreased intelligence)

69
Q

XYY male syndromes

A

No syndrome defined
learning difficulties, tall stature possible

70
Q

Klinefelter syndrome pathology

A

Male with extra X chromosome (XXY)
- Delayed puberty, tall stature, hypogonadism, obesity
- Decreased testosterone, elevated estrogen
- Usually sterile
1/1000 people

71
Q

What is X inactivation

A

One x chromosome is turned off, so one x produces most gene products.

72
Q

What is a barr body

A

inactive X forms barr body in females (have 2 x’s so one doesn’t matter)

73
Q

What is mosaicism caused from

A

nondisjunction in miotic division generates cells with chromosome abnormality

74
Q

What is a chimera

A

2 different cell lines fuse (2 twins conjoin and you get 1 person with different traits). Double fertilization.

Genetics (7 decks)

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