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IMAT > Genetics > Flashcards

Genetics Flashcards

1
Q

What is the error rate of the DNA replication?

A

About 1 in every 10^5 nucleotides

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2
Q

What is the error rate in in the synthesis of a complete DNA molecule?

A

1 in 10^10

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3
Q

What is a check point?

A

Regulated transition point in the cell cycle were negative signals can block progression to the next phase.
Sometimes include the signaling mechanisms that monitor cell cycle events and transmit the information to the control system.

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4
Q

What are the 3 main checkpoints during a cell cycle?

A
  1. ** G1 / S → the cell growth checkpoint **,
    Checks if the cell is big enough, sufficient nutrient, synthesized all the proper proteins before the s phase.
    Also checks for DNA damage - if there his negative “stop” signals, the cell enters resting phase (G0) until its or until it dies.
  2. ** G2 → DNA synthesis check point **
    Checks for adequate cell size and makes sure the DNA has been replicated correctly.
    If everything is good - mitosis
    If not - the cell goes through self destruction mechanism and dies
  3. ** M→ the spindle assembly checkpoint **
    Occurs between metaphase to anaphase transition point
    Checks to make sure there is chromosomal attachment to the spindle fibers from both poles.
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5
Q

Cell cycle control system

A

Controls the timing and coordination of cell cycle events.

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6
Q

Nucleotides

A

The monomers composing the nucleic acid
* Pentose - five carbon sugar, ribose/ deoxyribose
* nitrogenous base - carbon 1
* phosphate group - carbon 5

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7
Q

Phosphodiester bond

A

A condensation reaction
Nucleotide chains are formed by this reaction
The phosphate group is linked to the sugar
The backbone has directionality
5’ end → a free phosphate group
3’ end → a free OH group

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8
Q

DNA

A

Deoxyribose nucleic acid
* Contains all the information the cell needs to function & has the instruction on how to duplicate it
* polynucleotide located in the cell’s nucleus
* contain the instructions of protein synthesis
* the genome is formed by the number of DNA molecules and their size.

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9
Q

Deoxyribose

A

his sugar group is missing an oxygen on carbon 2

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10
Q

What is the structure of DNA?

A
  • Double strand molecule
  • the 2 strand are connected between the nitrogenous bases hydrogen bonds by y complementary base pairing:
  • adenine → thymine (2 bonds)
  • guanine → cytosine (3 bonds)
    Maintains a constant distance of except 3 carbon rings between the polynucleotide chains
    Allows the formation of the double helix structure
  • anti-parallel = 5’ end will always face the 3’ end
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11
Q

Primary structure of DNA

A

The linear sequence of nucleotides forming each strand
Linked by phosphodies for bonds

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12
Q

Secondary structure of DNA

A

The anti-parallel orientation of the strands (base pairing)
Linked by hydrogen bonds

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13
Q

Tertiary structure of DNA

A

3D structure
The double helix

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14
Q

How many base pairs each turn in the double helix contains?

A

10- 10.5 base pairs

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15
Q

Direction of the DNA twist

A

Right handed - clockwise screwing motion moves the helix upward
Left handed - anti clockwise screwing motion moves the helix upward

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16
Q

DNA packing

A

Refer to the level of compression and arrangement in which the DNA is found (depends on what stage in the cell cycle the DNA is found )

  1. DNA molecules are always wrapped around by histones
    8 histones are packed by a DNA molecule = nucleosome
  2. Chromatin = chain composed of many nucleosomes
  3. Chromosome = organized packing of chromatin → seen only when the cell prepares for divisions
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17
Q

Why is DNA drawn to histone?

A

They are drawn to each other by electrostatic force
Histones are positively charged proteins
DNA is negatively charged

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18
Q

How many Chromosome does the human cell contains?

A

46
Divided to 2 sets of 23 → one set from each parent
22 are autosomes
1 sex chromosome

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19
Q

Sex chromosome

A

X or Y
Female - XX
Male - XY

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20
Q

Homologous chromosomes

A

The 23 chromosomes pair.
Each pair contains genetic information that codes for the same characteristics.
The genes themselves are different

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21
Q

Sister chromatid

A

2 identical copies of the same chromosome ( nucleotide sequence is identical)
Happens after the duplication of DNA
Each duplicated chromosome Contains 2 double stranded DNA.
The two sister chromatids are linked together is a joining structure known as the centromere

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22
Q

Genetic code

A

3 letter code →” triplet code”

# universal
# has punctuations →
3 codes act as ‘full stops’ ( mark the end of a polypeptide coding sequence.
Some act as ‘start signals’ ( code TAC for methionine )
# redundant (some amino acids are encoded by more them one triplet ).

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23
Q

Cell cycle

A

Sequence of events that leads to the reproduction of the cell.
S phase - duplication (mainly chromosomes, other organelles are replicated throughout the cell cycle )
g1,g2 - growth
M phase - equal distribution

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24
Q

What are the stages of eukaryotic cell cycle?

A

Gap phases provide additional films for cell growth & serve as regulatory transition

G1 → gap phase, cellular contents (excluding chromosomes) are duplicated.
It has a swim or drown decision
S → 46 chromosomes duplicated
G2→ “double checking” the duplicated chromosomes for error, repairing
Mitosis → nuclear division
Cytokinesis → cell division (the membrane)

# G0 → prolonged non-dividing state
# interphase → G1 + S + G2

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25
Q

DNA replication

A

The process of the creation of another identical copy of all the DNA in the cell.
- happens only when the cell is close to dividing
- semi-conservative model of replication → the original strand and the new strand are joined together to form a new DNA molecule.
- starts in the ori (Origen of replication), the enzymes recognize the area and know to start breaking the hydrogen bonds there

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26
Q

Conservative replication

A

A completely new double helix is formed based on the “old” strand.
The old molecule remains completely separate from the new ones.

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27
Q

Semi conservative replication

A

Each new molecule is A combination of one old strand and one complete new.
- hydrogen bonds between the base pairs broken and this ‘unzips’ or unwinds the DNA double helix to form two single polynucleotide DNA strands that can act as template for the new strand.

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28
Q

Dispersive replication

A

Each DNA molecule contains both old and new parts that are scattered randomly throughout the polynucleotide chain.

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29
Q

Helices

A

Is an enzyme that breaks hydrogen bonds

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30
Q

DNA polymerase

A

Is an enzyme that is responsible for the new formation of the new strand.
- directionality: always synthesizes from 5’ to 3’
- add nucleotides to leading & logging DNA strands

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31
Q

Leading strands

A

→ 5’ to 3’, complementary to 3’ to 5’
→ replicated continuously
→ synthesized toward the replication fork

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32
Q

Legging strand

A

→ 5’ to 3’
→ opposite direction of the unzipping, synthesized away from the replication fork
→ not continuous
Copy a segment of unzipped DNA and then return to the beginning
→ create fragments of DNA called Okazaki fragments. They will link to one complete strand with the assistance of DNA ligase.

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33
Q

DNA ligase

A

Enzyme

# catalyzes the linkage of two neighboring nucleotides with covalent phosphodiester bonds during DNA replication to form the sugar - phosphate backbone of the newly synthesized DNA molecule

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34
Q

RNA primer

A

Short piece of RNA.
Binds to the 3’ end of the strand
Starting point of the replication, DNA polymerase cannot start without it.

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35
Q

DNA repair

A

Proofreading error-checking mechanisms.

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36
Q

DNA primase

A
  • Enzyme
  • generate RNA primers
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37
Q

What are the differences between the DNA of eukaryotic and prokaryotic?

A

** Location: **
# eukaryotic: nucleus + mitochondria + chloroplasts
# prokaryotic: a region in the cytoplasm called nucleoid region

** DNA packing: **
# eukaryotic: linear ( circular in the mitochondria & chloroplasts)
# prokaryotic: circular

** DNA quantity: **
# eukaryotic: a lot of DNA molecules in the nucleus. Bigger molecule, more bases
# prokaryotic: one double stranded DNA and a few plasmids

** DNA replication: **
# eukaryotic: a lot of ori’s, slower rate
# prokaryotic: one ori, faster rate, more mutations

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38
Q

Telomeres

A

The ends of the chromatids in chromosomes.
- ‘sealed’ with protective structure of the DNA
- prevent losing vital information during DNA replication

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39
Q

Telomerase

A

An enzyme that acts on the telomeres of chromosomes.
Preserve the length of chromosomes during cell division.
# retire primarily in cancer cells and reproductive cells.

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40
Q

Cell cycle

A

The sequence of events that occur in living cells and prepare the cell for division.

→ the life of the cell, from the moment its created to it’s division

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41
Q

Parent cell

A

The cell which performs the division.

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42
Q

Daughter cells

A

The new cells created from the division.
They are equal to each other in the genetic material

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43
Q

How long does the human cell division take?

A

24 hours
# 10-12 → S phase
# 11-13 → for growth ( G1 & G2)
#1 hour for the M phase

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44
Q

Mitosis

A

The process of nuclear division by which a genetically identical daughter nuclei are produced ( also identical to the parent nuclei)

Segregation of the 2 sets of chromosomes that are that are present in the cell after S phase.

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45
Q

What are the stages of mitosis?

A
  1. Prophase
  2. Metaphase
  3. Anaphase
  4. Telophase
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46
Q

Mitotic spindle

A

Pulls the sister chromatid apart and moves a complete set of chromosomes to each pole of the cell, where they are packaged into daughter nuclei.
→ microtubule fibers coming out of the centrosome, they span the length of the cell and they bind to the centromers and split the chromatids.

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47
Q

Kinetochore

A

Each chromatid carries it.

# A multiprotein complex that attaches the chromatid to microtabules connected to a spindle pole.
# proteins in the kinetochore help generate forces that drive chromosome movement.

48
Q

Prophase

A

Chromosomes condense and become visible

# spindle fibers emerge from the controsomes
# nuclear envelope breaks down
# controsomes move toward opposite poles.

49
Q

Metaphase

A

Chromosomes are lined up at the metaphase plate

# each sister chromatid is attached to a spindle fiber originating from opposite poles.

50
Q

Anaphase

A

centromers split in two

# sister Shrovetide are pulled toward opposite poles
# certain spindle fibers begins to elongate the cell

51
Q

Telophase

A

Chromosomes arrive at opposite poles and begin to condense

# nuclear envelope material surrounds each set of chromosomes
# the mitotic spindle breaks down

52
Q

Cytokinesis

A

A cleavage furrow separates the daughter cells

53
Q

Stem cell

A

A cell that can divide (by mitosis) an unlimited number of times.

→ every new cell has the potential to stay a stem cell or to develop info a specialized cell (blood cell or muscle cell, process called differentiation ).

54
Q

RNA

A

Ribonucleic acid
- polymer composed of nucleotide monomers linked by phosphodiester bonds (covalent)
- single strand nucleic acid
- it’s Penrose is ribose, has oxygen on carbon 2

55
Q

The central dogma

A

exception: reverse transcriptase ( RT ) enzyme - can take RNA and convert it to DNA (common in viruses).

“DNA makes RNA and RNA makes protein”
** DNA <—> RNA → protein **

DNA is in the nucleus, can’t leave. While, protein is synthesized in ribosomes outside of the nucleus.
RNA can move from the nucleus to the cytoplasm.

56
Q

What are the 3 main types of RNA relevant for protein synthesis?

A

mRNA → messenger RNA, involved in the transcription of DNA
tRNA → transfer RNA, has an important role in the translation component of protein synthesis
rRNA → ribosomal RNA, crucial role in ribosome structure.

57
Q

Transcription

A

The process by which DNA makes mRNA

58
Q

Translation

A

The process by which the message carried by mRNA is decoded to make protein

59
Q

RNA polymerase

A

Cars break the hydrogen bonds and synthesize the RNA molecule by the base of the DNA template (doesn’t need primer).
Build from 5’ to 3’

60
Q

Promoters

A

Specific sequence which mark when transcription starts

61
Q

Terminators

A

Specific sequences which mark where transcription ends.

62
Q

Transcription unit

A

The DNA stretch transcribed to RNA

63
Q

Genes

A

each DNA molecule contain many

# each gene encodes for a sequence of amino acid ( future protein)
#same specie will include the same genes

Not all the sequences in the DNA are genes

64
Q

Alleles

A

Different alleles are responsible for different traits of the same character.
Same gene, different nucleotide sequence.

65
Q

The process of transcription

A
  1. ** Initiation = ** the RNA polymerase recognizes the promoter, and binds to the DNA. He starts breaking the hydrogen bonds and that reveals the nucleotides.
  2. ** Elongation = ** extension of the molecule. RNA polymerase link nucleotides to synthesize RNA based on the DNA nucleotide sequence.
  3. ** Termination = ** the end of the transcription process, the RNA polymerase reached the terminator and releases itself from the DNA.

No Okazaki fragments are formed during RNA synthesis (only one strand is transcribed),

66
Q

Anti-sense strand

A

The template strand of the DNA
Serves as a template for specific mRNA synthesis

67
Q

Sense strand

A

The DNA strand which contain the gene sequence

68
Q

Post transcriptional modifications

A

Before the RNA exits the nucleus it does some modifications in order to survive in the cytoplasm.

5’ cap → addition of 1 guanine nucleotide to the 5’ end.

Polyadenylation ( poly-a-tail) → addition of 50 - 250 adenine nucleotides to the 3’ end

Introns → removed from the chain and stay in the nucleus

69
Q

RNA splicing

A

The process of removing major non-coding parts of the RNA chain.
Introns - removed and stay in the nucleus
Exons - leave the nucleus, and stay in the mRNA molecule

70
Q

Ribosome

A

The organelle were translation is carried out (in the active site)

Composed of 2 subunits and rRNA:
Prokaryotic 70S → large- 50s, small - 30s
Eukaryotic 80s → large- 60s, small- 40s

71
Q

Codon

A

3 nucleotides group in the mRNA
Each codon encodes for one amino acid.
64 combinations of genetic code overl

72
Q

Start codon

A

AUG
Methionine

73
Q

Stop codons

A

UAA →u are annoying
UAG → u are gone
UGA → u go away

74
Q

tRNA

A

Transfer RNA
- small RNA molecule
- distinctive folded structure with 3 hairpin loops (shape: three-leafed clover)
- one hairpin loop contain a sequence called anticodon ( recognize & decode mRNA codon)
- has a region at the end where amino acid binds
- 61 kinds of tRNA

Each tRNA translates a specific mRNA codon to a specific amino acid.

75
Q

The process of translation

A
  1. ** initiation ** = the ribosomes connects and reads the mRNA until it gets to the AUG (methionine), where he can start translating.
  2. ** elongation** = the ribosome reads on the mRNA making the polypeptide sequence with the help of the tRNA (anticodon)
  3. ** termination ** = the ribosome reads the ‘stop’ codon and stop coding the mRNA
76
Q

What is the definition for alleles?

A

Genes which encodes for the same character but differ in nucleotide sequences.
Diploid creatures contain 2 alleles for each character.
Two alleles for the same gene/character can be different from each other.

77
Q

What is a homozygous?

A

When the 2 alleles of a gene are the same
Can be dominant or recessive.

78
Q

What is a heterozygous?

A

When 2 alleles of a gene are different

79
Q

What is a genotype?

A

The alleles future relevant for the genetic information

80
Q

What is a phenotype?

A

The set of observable visible physical traits.
The genotype determines the phenotype.

81
Q

What is the definition of true breeding?

A

An organism that always passes the same phenotype trait, refers to a specific trait.
It must be homozygous for that trait.

82
Q

What is the definition of hybrid?

A

Also known as crossbreed
The result of combination of qualities of two different breeds.

83
Q

Define P generation when crossing

A

The parents

84
Q

Define F1 generation when crossing

A

The offspring of the P generation.
And the P generation of the F2 generation…

85
Q

What is the law of segregation?

A

The two alleles for a heritable character segregate during gamete formation and end up in different gametes → each gamete gets only one allele of the gene.

86
Q

Why did Mendel experiment on plants?

A

Their life cycle is shorter
They have a lot of offsprings ( allowed him to do a lot of experiment on different subjects )

87
Q

What was Mendel focus in his experiments?

A

Characters with 2 phenotypes only ( flower color and size, pea shape… ).
Only true breeding plants.

88
Q

What is the monohybrid cross?

A

A cross between 2 true breeding, when only one character is being studied.

89
Q

What was the main conclusion of Mendel’S experiment in monohybrid crossing?

A

The “heritable factor” for the white flower wasn’t lost or blended, only “masked”.
→ dominant allele (D)
→ recessive allele (d)
If an organism is hetrozygote, the dominant allele will determine the phenotype.
To see recessive allele, we need two recessive alleles (dd).

Each organism genotype contains 2 alleles for each character:
# homozygote organism - identical alleles
# hetrozygote organism - different alleles

90
Q

What does the law of segregation claim?

A

The two alleles for a heritable character segregate during gamete formation and end up on different alleles.

91
Q

What is a Punnett square?

A

A graphic representation of the offspring that could be.

92
Q

What is the ratio of the phenotype of the F2 generation in monohybrid crossing?

A

3:1 → ( dominant: recessive )

93
Q

What is the ratio of the genotype of the F2 generation in monohybrid crossing?

A

1:2:1→(PP:Pp:pp)

94
Q

What does Mendel’S law of independent assortment state?

A

Each pair of allele segregates independently of the other pairs of alleles during gamete formation.
The inheritance of one character has no effect on the inheritance of another character.

95
Q

What are dihybrid crosses?

A

A kind of crossing examining two characters in the same time

96
Q

What happened during Mendel’S dihybrid crossing experiment?

A

Yellow and round seeds → alleles are dominant
Green and wrinkled seeds → alleles are recessive

F1 generation: yellow and round phenotype ( YyRr )
F2 generation: 4 different phenotypes ( yellow and round, yellow and wrinkled, green and round, green and wrinkled )

97
Q

What is the ratio of the phenotype of the F2 generation in dihybrid crossing?

A

9:3:3:1 ( at least 2 dominant alleles: 1 dominant allele: 1 dominant allele: recessive alleles )

98
Q

What is a testcross?

A

A way to discover an individual genotype by fertilizing the dominant phenotype organism with homozygote recessive genotype.

99
Q

What will be the result in a test cross, it the original phenotype was hetrozygote?

A

Offspring ratio 1:1
Dd, dd, dd, Dd

100
Q

What will be the result in a test cross, it the original phenotype was homozgote?

A

Only one phenotype
Dd

101
Q

What is the cell cycle control system?

A

A network of regulatory proteins that control the timing and coordination of cell cycle events.
And it merges extracellular and intracellular signals before approving division.

102
Q

What controlled the progression between the different stages in the cell cycle?

A

” Stop signs “ - checkpoints

103
Q

How many checkpoints are in the cell cycle?

A

3 main checkpoints:
1. G1- swim or drown
2. G2 - DNA synthesis checkpoint
3. M - the spindle assembly checkpoint

104
Q

How the process of transcription occurs?

A
  1. Initiation → RNA poly recognize promotor & binds to DNA ( breaks hydrogen bonds )
  2. Elongation → extension of the molecule
  3. Termination → RNA poly reach the terminator and frees itself from the DNA
105
Q

What is the anti-sense strand?

A

The DNA strand that serves as a template for specific mRNA synthesis.
( the complementary strand of the gene sequence).

106
Q

What is the sense strand?

A

The duh strand that contains the gene sequence

107
Q

Where are nucleotides added during transcription? (Directionality)

A

RNA poly adds nucleotides to the 3’ end of the chain.
# RNA formed 5’ → 3’
#DNA read from 3’ → 5’

108
Q

Why aren’t Okazaki fragments formed during RNA synthesis?

A

Because only one strand is transcribed, the leading strand.

109
Q

What modifications occur on the RNA in order to survive the cytoplasm?

A

5’ cup → addition of 1 guanine nucleotide to the 5’ end.

# poly-A- tail → addition of 50 -250 adenine nucleotides to the 3’ end.
# RNA splicing → the process of removing major non coding parts of the RNA chain ( introns removed, exons fused together ).

110
Q

What are introns?

A

Non-coding parts of the RNA chain, that are removed during RNA splicing.

111
Q

What are exons?

A

The coding parts of the RNA, leaves the nucleus, and stay in the mRNA molecule.

112
Q

What are ribosomes?

A

The organelle that responsible for translation.

113
Q

What composes ribosomes?

A

2 subunits and rRNA:
# Prokaryotic 70 s→ large = 50 s, small = 30 s
# eukaryotic 80s → large = 60 s, small = 40 s

114
Q

What happens during translation?

A
  1. Initiation → the ribosomes connect and reads the mRNA until it gets to the AUG (methionine) sequence.
  2. Elongation → ribosomes read mRNA making the polypeptide sequence with the help of the tRNA anticodon.
  3. Termination
115
Q

What are polyribosomes?

A

mRNA with a lot ot ribosomes connected to it

116
Q

What are reading frames?

A

A way of dividing the sequence of nucleotides in a nuclei acid molecule info a set of consecutive, non overlapping triplets.
Each frame changes the sequence of amino acid created.

117
Q

What are the differences between eukaryotic and prokaryotic protein synthesis?

A

Location of transcriptions
Pro: cytoplasm
Eu: nucleus

modifications
Pro: non
Eu: 5’ cap, poly-a- tail

** order of synthesis**
Pro: may occur simultaneously
Eu: transcription ends and translation starts

** transcription factors**
Pro: without
Eu: with

IMAT (32 decks)

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