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Flashcards in Intro to Medical Genetics Deck (64)
1

A gene is a segment of DNA that encodes for a specific
a) protein
b) tRNA
c) rRNA
d) microRNA
e) all of the above

e

2

Define an allele

Alternative forms of a gene (DNA at a specific locus) that differ in sequence

3

Define a locus

A physical region of a chromosome; often used to refer to a segment of DNA that contains a specific gene

4

Homologous chromosomes are chromosomes that ______ during meiosis, ____ from each parent

pair, one

5

Are homologous chromosomes identical?

No, normally only a few base pair differences in each gene

6

Are sister chromatids identical?

Yes, two identical duplicated chromosomes joined by a single centromere

7

During which cell replication cycle would you find sister chromatids?

Metaphase

8

What are autosomes?

ANy chromosome that is not a sex chromosome

9

An organism with 4 copies of each chromosome would be ________

tetraploid

10

A human has 45 chromosomes in a cell. He is a _____________ (type of ploidy)

Aneuplod

11

A human has 69 chromosomes in a cell. He is a ____________ (type of ploidy)

Euploid - abnormal but still same number of each homologous chromosome

12

Germline cells are responsible for _____________________

production of gametes

13

What are gametes

haploid germ cells (sperm and ova)

14

What are zygotes

Two gametes fuse (during fertilization), diploid

15

Homologous chromosomes have _______ genes in ______ positions, but _______ alleles
(same/different)

same, same, different

16

Why is neonatal screening done?

To ID rare disorders that can cause brain damage or death if not treated early ie PKU

17

Describe prophase of mitosis

chromatin condenses (chromosomes with two chromatids) --> spindle forms --> nucleolus breaks down

18

Describe prometaphase of mitosis

spindle invades nuclear region, chromosomes move to equatorial plane

19

Describe metaphase of mitosis

Chromosomes at equatorial plane and centromeres divide

20

Describe anaphase of mitosis

poles move apart and chromosomes move towards destinations

21

Describe telophase of mitosis

Spindle breaks down --> chromatid uncoils --> nucleoli formed --> contractile ring causes cytokinesis

22

What is the product of cytokinesis in mitosis?

Two daughter cells, each genetically identical to parent cell

23

Describe prophase I of meiosis

Homologous chromosomes pair up and exchange fragments (cross over)

24

Describe metaphase I of meiosis

Homologous pairs line up at metaphase plate

25

Describe Anaphase I of meiosis

Homologues separate to opposite ends of cell, sister chromatids stay together

26

Describe Telophase I of meiosis

Newly formed cells are haploid, each chromosome has two (non-identical) sister chromatids

27

Meiosis II is very similar to mitosis. What are the two differences?

1) Haploid (2n) cells at beginning rather than diploid (4n)
2) Creates 4 haploid cells, with chromosomes having one chromatid each

28

What is the key difference between meiosis and mitosis?

During prophase homologous chromosomes synapse - pair up tightly and there is genetic exchange (evidenced by chiasmata)

29

Describe synapsis

Pairs of sister chromatids align according to homologous sequences and are bound together --> crossing over occurs

30

What is the product of crossing over? (type of chromosome)

recombinant!

31

What are the 4 components of gene structure?

1) promoters
2) coding sequences (exons)
3) introns
4) structural regions (non-transcribed, 5' and 3' untranslated sequences)

32

What causes genetic disorders
a) changes in DNA
b) changes in RNA
c) changes in protein level/activity

c

33

What type of mutation in Hgb causes sickle cell anemia?

single base pair change

34

Function of promoter sequence

controls levels of mRNA expression --> controls protein expression

35

Function of introns

"intervening sequences"
interrupt coding sequences
spliced out

36

Function of exons

Coding sequences
Specific sequence of AA in proteins

37

Function of structural regions

Untranscribed regions
5' and 3' untranslated regions in mRNA

38

The TATA box is a promoter sequence that specifies to other molecules ____________________

where transcription begins

39

The CCAAT box is a distinct pattern of nucleotides with consensus sequence that occur upstream by ___________ bases to _______________

60-100, initial transcription site

40

The core basal promoter determines ______ site for transcription and ____________

start, whether transcription occurs

41

Describe the function of an enhancer

Short region of DNA that can be bound by activator proteins to increase the likelihood that transcription of a particular gene will occur

42

Tissue specific elements say _____ and _____ a gene is transcribed

when and where

43

Describe the function of regulatory elements

Determine when, where and how much transcription occurs

44

Intron mutations are usually harmful, true or false

False, only mess things up when located in splice zone

45

What percentage of a gene is not transcribed?

70%

46

What percentage of a transcript is structural?

70%

47

All combos beginning with CG will produce ______

ARGININE

48

A point mutation that does not change the amino acid is called a

silent mutation

49

A point mutation that does change the amino acid, but only to another with similar biochemical properties is called a

missense mutation

50

A point mutation that introduces a premature stop codon

nonsense mutation --> truncated protein

51

Does the addition of 3 nucleotides qualify as a frame shift mutation?

no. Can still be harmful examp: delta f508

52

A promoter mutation would affect _______

levels of protein expression

53

Tertiary post translational processing involves

Interdomain interactions

54

Quartanery post translational processing involves

multiple polypeptide complexes

55

Loss of function mutations lead to (2)

inactive protein products OR loss of expression

56

PKU and Cystic Fibrosis are examples of haplosufficiency diseases. What does this mean?

One normal allele is enough to not have disease
DOMINANT

57

Familial hypercholesteremia is a haploinsufficiency disease. What does this mean?

One bad allele and you're f**ked
RECESSIVE

58

Gain of function mutations lead to (2)

new protein product OR overexpression/misexpression (in wrong tissue of a normal protein

59

Huntington's Disease and the trisomies are caused by what type of mutation?

gain of function

60

Osteogenesis Imperfect II is an example of a dominant negative disease. What does this entail?

Mutant protein inhibit activity of normal protein

61

What does it mean to be reproductively lethal?

Organism can have mutation and live with it but cannot pass it on to next generation

62

Reproductively lethal mutations are always ______

spontaneous and new

63

Recessive disorders are always spontaneous new mutations, true or false

FALSE - rarely, X linked disorders present a special case

64

What are the three ways a silent mutation can occur

1) in non essential sequences (introns, untranslated structural regions)
2) occur in redundant base (no AA change)
3) result in a conservative substitution that does not change protein structure or function