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Medical Genetics > Central Dogma > Flashcards

Central Dogma Flashcards

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USMLE® Step 1 flashcards Biology 101 flashcards
1
Q

Mitosis vs meiosis

A

Mitosis - production of somatic cells
Growth, differentiation, repair

Meiosis - production of gametes
Somatic cells are diploid (2N)
Gametes are haploid (1N)

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2
Q

MITOSIS AND MEISOSIS ARE NOT CELL DIVISION THEY ARE NUCLEAR DIVISION

A

CYTOKENISIS IS CELL DIVISION

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3
Q

What is interphase?

A

Mitosis only occupies small portion of cell’s life cycle
Interphase - period between mitoses
Where most cellular activities are performed

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4
Q

What are the components of interphase?

A 
Interphase is broken into sub-phases:
G1 - period of rapid growth and development
S - synthesis phase
G2 - final growth and prep for M phase
M phase - mitosis and cytokinesis
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5
Q

Cell cycle progression is controlled by ______?

A 
Cell cycle progression is controlled by checkpoints
G1 checkpoint
G2 checkpoint
M checkpoint
Length of cell cycle varies
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6
Q

Mitosis

nuclear division
chromosome segregation

A

Nuclear division - each daughter cell receives an equal and equivalent set of chromosomes

Chromosome segregation - distributing a copy of each chromosome to each daughter cell

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7
Q

Phases of mitosis

Please
Put 
Me
Adjecent 
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Cat
A

Prophase - chromosome condensation, formation of centrosomes (made of pair of centrosomes) that control centrioles
Prometaphase - nuclear membrane falls apart
Metaphase - chromosomes undergo congression
Anaphase - centromeres split - chromosome migration
Telophase - nuclei reform
Cytokinesis - cytoplasmic division

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8
Q

Human Karyotype

  • analyse how?
  • function of centromere
A

Analyze metaphase chromosomes based on size, shape, staining pattern, centromere position

Centromere separates P arm from Q arm
P arm: short arm
Q arm: long arm

Used to readily determine structural or numerical abnormalities

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9
Q

Diploid cells becoming what?
1 round of DNA synthesis but ___ (seperate from mitosis)

Meiosis 1 - vs Meiosis II-

A

Diploid cells becoming haploid gametes

1 round of DNA synthesis - 2 nuclear/cytoplasmic divisions

Meiosis 1 - reduction division and genetic recombination
Meiosis II - similar to mitosis

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10
Q

Meiosis I
Prophase I
Tetrads form

Metaphase I -
Anaphase I -
Telophase I -
Meiosis II -

A

Meiosis I
Prophase I - homologous pairs synapse
Tetrads form - chiasmata - points of crossing over
Metaphase I - tetrads align
Anaphase I - homologues separate
Telophase I - nuclear envelopes reform
Meiosis II - similar to mitosis, but with 1N cells

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11
Q

Medical relevance of cell division

Cell division maintains chromosome number across generations

Errors in either mechanism will lead to cell lineage with abnormal numbers of chromosomes

Responsible for spontaneous abortions, developmental defects, failure to thrive, mental retardation

A

yikes :(

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12
Q

Genes are capable of generating multiple different proteins

Alternative splicing, biochemical mods

A

Individual proteins do not function by themselves

~25,000 genes might make ~1,000,000 proteins

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13
Q

Genes located throughout genome but do tend to cluster

Some genes organized into families of related genes

Genes on autosomes - 2 copies of each
Both usually expressed to generate product

A

ok ok ok :D

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14
Q

What is central dogma

A

DNA → RNA → protein

Genetic information stored as genetic code
Sequence of nucleotides determines sequence of amino acids
DNA is transcribed into mRNA
mRNA is translated into polypeptide

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15
Q

DNA vs RNA

A

RNA - structure similar to DNA
Ribose vs deoxyribose
Uracil vs thymine
Single vs double-stranded

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16
Q

What is a gene

A

Gene - portion of DNA containing code for the aa sequence of a polypeptide chain, and the regulatory sequences necessary for its expression

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17
Q

what is a gene used for?

A

sequence of DNA that is required for the production of a functional product
Includes coding & adjacent sequences
Adjacent sequences necessary for expression

18
Q

Promoter

which end of gene
function?

what are some other regulatory elements of genes?

A

at 5’ end - required for initiation of transcription

Helps to regulate tissue specificity

Other regulatory elements: enhancers, silencers, locus control regions
3’ end contains signal for polyA tail addition

19
Q

What are gene families?

A

Gene families share closely related DNA sequences - closely related polypeptides
β-globin gene cluster on chromosome 11
OR family - throughout genome

20
Q

What are pseudo genes?

A

found in gene families

They non-coding due to mutations

Non-processed - dead genes
Processed - no introns
Non-coding RNA genes

21
Q

What controls the process of transcription?

A

Transcription initiation under control of transcription factors

22
Q

How do transcription factors work?

A

they interact with specific DNA sequences to determine spatial and temporal pattern of expression

23
Q

Which direction does transcription begin?

A

Begins at 5’ UTR - continues through introns and exons

24
Q

What is removed as the before the final mRNA product?

A

5’ and 3’ modifications occur, introns removed, exons spliced - forms mRNA
mRNA transported to cytoplasm
Translation uses ribosome and tRNA

25
Q

What is the function of the cap and the tail?

A

Need cap to go to cytoplasm

Tail increases stability of molecule—otherwise degreades quickly

26
Q

What direction is DNA read in transcription?

What direction is RNA procudced?

A

DNA read in 3’-5’

RNA produced at 5’-3’

27
Q

Coding strand vs non coding strand?

A

Untranscribed DNA strand - coding strand

Transcribed strand - non-coding (anti-sense)

28
Q

How is the primary RNA transcript modified?

A

Addition of 5’ cap

Polyadenylation of 3’ end (AAUAAA)

mRNA transported to cytoplasm

29
Q

Where does rna splicing/processing occur?

A

All post processing and RNA splicing occurs in nucleus

30
Q

What molecule is required for translation

Where is the site of protein synthesis - composed of rRNA and protein

A

tRNA

Ribosomes - site of protein synthesis
Composed of rRNA and protein

31
Q

Genetic code is what?

Consist of ?

A

degenerate

codons

32
Q

AUG

A

start codons

33
Q

UGA
UAA
UAG

A

stop codons

34
Q

β-Globin Gene

A

146 aa polypeptide from 1.6 kb gene

3 exons - 2 introns

DNA sequences for initiation are ~200 bp upstream of start site

35
Q

The β-Globin Gene only expressed in which type of cells?

A

erythroid cells?

36
Q

β-Globin Gene

A

TATA & CAT not found in all promoters
Usually in tissue specific genes
Housekeeping genes contain CpG islands
β-globin gene also has enhancers
Activating sequences several kb from gene

37
Q

β-Globin Gene

RNA splicing

A

RNA Splicing - must remove 2 introns
Exact and efficient process - guided by sequences in 3’ and 5’ ends of introns
5’ end GT - 3’ end AG

38
Q

The β-Globin Gene

A

Alternative Splicing - found in many genes - not β-globin
Multiple splicing patterns
Can create multiple, related mRNAs from single gene
1/3 of human genes

39
Q

What is polyadenylation?

A

Polyadenylation - mature mRNA contains 130 bp of 3’ UTR between stop and polyA tail
Cleavage of 3’ end and addition of polyA tail controlled by AAUAAA 20 bp upstream of polyA site

40
Q

Variations in Expression: relevance to medicine

A

All control levels participate in proper regulation of expression

Replication and segregation, gene structure, transcription, RNA splicing, mRNA stability, translation, protein processing, protein degradation

Changes have little effect on some genes - major effects for others

41
Q

Describe the parts of interphase?

G1 phase

G1 Checkpoint

S Phase

G2 Phase

G2 Checkpoint

A

o Interphase – period between mitoses where most cellular activities are performed

 G1 phase – period of rapid growth and development
• 10-12 hrs

 G1 checkpoint – point of no return, check if we need cells and if we have enough nutrients to make some
• If doesn’t pass, goes into G0

 S phase – DNA synthesis
• 6-8 hrs

 G2 phase – final growth and prep for M phase
• 2-4 hrs

 G2 checkpoint – check if the DNA was copied correctly, if yes, fix itself or die!

Medical Genetics (4 decks)

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