Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

USMLE Step 1 - Kaplan lecture notes 2019 > Biochemistry and medical genetics > Flashcards

Biochemistry and medical genetics Flashcards

You may prefer our related Brainscape-certified flashcards:
USMLE® Step 1 flashcards
1
Q

Definition of transcription

A

transfer of information from DNA to RNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Definition of translation

A

transfer of information in the RNA base sequence to the amino acid sequence of a protein (RNA → PROTEIN)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

In what phase does DNA replication occur

A

S-phase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Definition of the M phase

A

it is the time in which the cell divides to form 2 daughter cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Definition of Interphase

A

Describes the time between 2 cell divisions of mitoses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

T/F: Gene expression occurs throughout all stages of interphase

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How is Interphase divided and what does happens in each of those phases

A

G0: cells that have stopped cycling, such as muscle and nerve cells, are said to be in this state

G1 phase (gap 1): cellular growth preceding DNA synthesis

S phase (DNA synthesis): DNA replication occurs
- at the end of S phase each chromosome has doubled its DNA content and is composed of 2 identical sister chromatids linked at the centromere

G2 phase (gap 2): period of cellular growth after DNA synthesis but preceding mitosis. Replicated DNA is checked for any errors before cell division

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What phase of the cell cycle target the following chemotherapeutic agents: methotrexate, 5-fluoruoracil and hydroxyurea

A

S phase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What phase of the cell cycle target the following chemotherapeutic agents: bleomycin

A

G2 phase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What phase of the cell cycle target the following chemotherapeutic agents: paclitaxel, vincristine, vinblastine

A

M phase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What phase of the cell cycle target the following chemotherapeutic agents: cyclophosphamide, cisplatin

A

They are non cell-cycle specific

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are the names of the proteins that ensure that cells will not enter the next phase of the cycle until the molecular events in the previous cell cycle phase are concluded

A

cyclins and cyclin-dependent kinases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

T/F: Reverse transcription is more commonly associated w/ life cycles of retroviruses

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are nucleic acid assembled from?

A

nucleotides, which consist of 3 components:

  • nitrogenous base
  • 5 carbon sugar (pentose)
  • phosphate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the 2 types of nitrogen-containing bases commonly found in nucleotides?

A

purines and pyrimidines

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

structural characteristics of purines

A

they contain 2 rings in their structure

17
Q

what are the purines commonly found in nucleic acids

A

adenine and guanine

18
Q

structural characteristics of pyrimidines

A

have only 1 ring

19
Q

What are the pyrimidines? commonly found in nucleic acids

A

Cytosine (DNA & RNA)
Thymine (DNA)
Uracil (RNA)

20
Q

What is the pyrimidine that is only found in RNA

A

Uracil

21
Q

What is the pyrimidine that is only found in DRA

A

Thymine

22
Q

How are nucleosides formed

A

They are formed by covalently linking a base to the number 1 carbon of a sugar

23
Q

How are nucleotides formed

A

They are formed when 1 or more phosphate groups is attached to the 5 carbon nucleoside

24
Q

T/F: In Nucleic Acids, a phosphate group links the 3’ carbon of a sugar to the 5’ carbon of the next sugar (3’, 5’ phosphodiester bonds) and have distinct 3’ and 5’ ends, thus polarity

A

TRUE

25
Q

T/F: Nucleic Acids sequence is always specified 3’ → 5’

A

False!

It is always specified as 5’ → 3’

26
Q

What are the properties ofChargaff’s rules

A

The amount of A equals the amount of T, and the mound of G equals the amount of C. Thus, total purines equals total pyrimidines

27
Q

What does Adenine pair with and with how many hydrogen bonds

A

Thymine (w/ DNA) … Uracil (w/ RNA)

and with 2 hydrogen bonds

28
Q

What does Guanine pair with and with how many hydrogen bonds

A

Cytosine

and with 3 hydrogen bonds

29
Q

What can cause a double-helical DNA to be denatured

A

Conditions that disrupt hydrogen bonding and base stacking (no covalent bonds are broken in this process)

Heat, alkaline pH, and chemicals such as formamide and urea are commonly used to denature DNA

30
Q

Can denatured single-stranded DNA be renatured?

A

Yes, if the denaturing condition is slowly removed

31
Q

What enzymes can change the amount of supercoiling in DNA molecules

A

Topoisomerases

32
Q

what is negatively supercoiled DNA

A

DNA that is wound more loosely than in Watson-Crick DNA. This form is required for most biologic reactions

33
Q

What is positively supercoiled DNA

A

DNA is wound more tightly than in Watson-Crick DNA

34
Q

What is the basic packing unit of chromatin

A

nucleosome

35
Q

What are nucleosomes made of and what function does Histone H1 have?

A
  • 2 copies of histones: H2A, H2B, H2, and H4 (they aggregate to form the histone octamer that the DNA wraps around
  • a series of nucleosomes is sometimes called “beads on a string” but is more properly referred to as a 10nm chromatin (it is more “opened” than the 30nm fiber)
  • Histone H1 is associated with the linker DNA found between nucleosomes to help package them into a solenoid-like structure, which is a thick 30nm fiber
36
Q

What are the types of chromatin that cells in interphase have?

A

Euchromatin: more opened and available for gene expression
Heterochromatin: much more highly condensed and associated w/ areas of the chromosomes that are not expressed

37
Q

During what phase of the cell cycle is the chromosome structure visible

A

Mitosis

38
Q 
Endonuclease activation and chromatin fragmentation are characteristic features of eukaryotic cell death by apoptosis. Which of the following chromosome structures would most likely be degraded first in the apoptotic cell?
A) Barr body
B) 10nm-fiber
C) 30nm-fiber
D) Centromere
E) Heterochromatin
A

B) 10nm-fiber
- the more “opened” the DNA, the more sensitive it is to enzyme attack. The 10-nm fiber, w/o the H1, is the most open structure listed. The endonuclease would attack the region of unprotected DNA between the nucleosomes

39
Q 
A medical student working in a molecular biology laboratory is asked by her mentor to determine the base composition of an unlabeled nucleic acid sample left behind by a former research technologist. The result of her analysis showed 10% adenine, 40% cytosine, 30% thymine, and 20% guanine. What is the most likely source of the nucleic acid in this sample? 
A) Bacterial chromosome
B) Bacterial plasmid
C) Mitochondrial chromosome
D) Nuclear chromosome
E) Viral genome
A

E) Viral genome
- a base compositional analysis that deviated from Chargaff’s rules (%A=%T, %C=%C) is indicative of single-stranded, not double-stranded, nucleic acid molecule. All options listed except E are examples of circular or linear DNA double helices. Only a few viruses (Ex: parvovirus) have single-stranded DNA

USMLE Step 1 - Kaplan lecture notes 2019 (1 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions