bio final Flashcards
(117 cards)
1
Q
true or false? a haploid organism has one pair o homologous chromosomes
A
false
2
Q
when do sister chromatids f each chromosome separate meiosis
A
meiosis ii
3
Q
what is an x shaped structure formed from the crossing over of homologous chromosomes, which can then exchange segments at the crossover sites
A
chiasma
4
Q
what is the composition of a tetrad at the beginning of prophase i
A
one pair of homologous chromosomes
5
Q
what is a tetrad
A
one chromosome in a tetrad is paternally inheretid, while the other is maternally inherited. each chromosome consists of two chromosomes
6
Q
when do sister chromatids separate meiosis
A
anaphase ii
7
Q
synapsis
A
pairing of homologous chromosomes that occurs during prophase i
8
Q
when do homologous chromomsomes migrate to opposite poles
A
anaphase i – the sister chromatids remain attached at their centromeres
9
Q
HOW DO CELLS AT THE COMPLETION OF MEIOSIS COMPARE WITH THE CELLS THAT ARE IN PROPHASE OF MEIOSIS I
A
THEY HAVE HALF THE NUMBER OF CHROMOSOMES AND one-fourth the amount of dna
10
Q
sister chromatids separate from each other during when
A
mitosis and meiosis ii
11
Q
what syndrome is characterized by the xo chromosome abnormality
A
turner syndrome
12
Q
when can nondisjuntion occur
A
- in mitosis or meiosis, when sister chromatids fail to separate
- in meiosis, when homologous chromosomes fail to separate
13
Q
what type of chromosome abnormality is most likely to be viable in humans
A
trisomy
14
Q
short segments of newly synthesized DNA are joined into a continuous strand by
A
ligase
15
Q
the first step in the replication of DNA is catalyzed by what
A
helicase (unwinds double helix)
16
Q
what catalyzes DNA synthesis
A
DNA polymerase
17
Q
what enxyme is important for relieving tension in a helix as it unwinds during DNA synthesis
A
topoisomerase
18
Q
when are single stranded DNA molecules antiparallel
A
when they are lined up next to each other but oriented in opposite directions
19
Q
what does a single-strand binding protein do, and where does it bind
A
prevents H-bonds between bases, binds after the replication fork
20
Q
eukaryotic telomeres replicate differently than the rest of the chromosome. THis is a consequence of what
A
the gaps left at the 5’ end of the lagging strand
21
Q
if newly synthesized DNA is found in fragments, whta isnt working
A
ligase
22
Q
what is a major difference between eukaryotic DNA replication and prokaryotic DNA replication
A
projaryotic chromosomes have a single origin of replication, whereas eukaruptic chromosomes have multiple origins of replication
23
Q
where does telomerase bind
A
the overhang at the end of the chromosome
24
Q
template for telomerase
A
RNA template
25
what does a nonsense mutation do
leads to early termination of protein synthesis
26
when does protein synthesis end
when a sop codon is produced
27
what does a silent mutation do
results in the insertion of the same aminio acid as was coded for by th eoriginal sequence
28
base subsitution mutations alter a what
nucleotide
29
a missense mutation does what
dramatically alter protein structure
30
what untwists a portion of the DNA double helix for RNA transcription
RNA polymerase
31
region of DNA at which the process of transcription begins
the promoter
32
site in dna that recruits the rna polymerase
promoter
33
nontranscribed region of a gene
promoter
34
where are ribosomal subutits formed
nucleolus
35
where does transcription and RNA processing occur
nucleus
36
interons are removed from the pre RNA by what
snRNAs
37
what is added to the 5' end of the pre-mRNA
a cap consisting of a modified guanine nucleotide
38
what is added to the 3' end of the pre-mRNA
a poly-A tail (50-250 adenine nucleotides)
39
in eukaryotic cells, transcription cannot begin until when
several transcription factors have bound to the promoter
40
the -10 box and the -35 box two regions of a bacterial promoter do what
bind to the sigma subunit that is associated with RNA polymerase
41
how does termination happen
when release factors recognize the stop codon in the A site and catalyze the release of the polypeptide from teh tRNA in the P site
42
what enxyme catalyzes the attachment of an amino acid to tRNA
aminoacyl-tRNA synthetase
43
the initiator tRNA attaches at the ribosome's what site
P
44
where does amino acid bind to a tRNA
the part that sticks out at the 3' end
45
where do regulatory proteins bind in bacteria
the operator
46
in lac operon what is the regualtory gene
lacI
47
why are the genes involved in lactose metabolism considered to be an operon
they are all controlled by the same promoter
48
addition of what short proteins in eukaryotes target proteins for destruction by protasom
ubiquitins
49
enzyme complexes that break down protein are called what
proteasomes
50
protein-phosphorylating enzymes' role in the regulation of gene expression involves what
protein activation
51
is acetylation of histone tains reversable
true
52
what is used to coordinate the expression of multiple related genes in eukaryotic cells
the genes share a common enhancer, which allows appropriate activators to turn on their transcription at the same time
53
how does a microRNA recognize a specific target mRNA
a microRNA can recognize a specific target wherever it can form complementary base pairs with the target
54
can mutations that occur in somatic cells be passed on to offspring
no
55
what separates during anaphase i
homologous chromosomes
56
crossing over contributes genetic variability between what
homologous chromosomes
57
what synthesizes short segments of RNA
primase
58
what covalently connects segments of DNA
ligase
59
which of the enzymes remove the RNA nucleotides from the priner and add equivalent DNA nucleotides to the 3' end of Okazaki fragments
DNA polymerase I
60
Benzopyrene in cigarette smoke binds to DNA and distorts its shape, interfering with DNA replication. Which repair mechanism would most likely be used to repair the damage caused by this chemical
nucleotide excision repair
61
transcription of the structural genes in an inducible operon
starts when the pathway's substrate is present
62
suppose an experimentser moves the operator to the far end of the operon, past the transacetylase (lacA) gene, what would likely occur when the cell is exposed to lactose
the structural genes will be transcribed continuously
63
for a repressible operon to be transcribed, what must occur
RNA polymerase must bind to the promoter, and the repressor must be inactive
64
in eukaryotes, general transcription factors do what
bind to other proteins or to a sequence element within the promoter called the tata box
65
what is used to coordinate the expression of multiple related genes in eukaryotic cells
a specific combo of control elements in each gene's enhancer coordinates the simultaneous activation of the genes
66
what is a karyotype and what can it be used for
visual representation of an individuals complete set of chromosomes, allowing doctors to examine number and structure of chormosomes in cell to identify potential genetic abnormalities
67
what is meant by diploid and haploid
diploid has two complete sets of chromosomes, wchih is the case for most human body cells. haploid only has one set of chromosomes
68
what is aneuploidy
aneuploidy has only one extra or less chromosomes-- partial set of chromosomes
69
what is polyploidy
extra complete sets of chromosomes
70
what are non-sister chromatids
belong to homologous chromosomes within a pair from differnt parents
71
how many alleles do you have for one gene
2
72
what is the difference between incomplete and codominance
incomplete is a mix, while codominance both appear together without blending
73
what is epistasis
expression of one gene is altered by the expression of one or more other genes
74
when more than one gene is responsible for a phenotype, the trait is said to be
polygenic
75
when one gene has multiple phenotypic effects it is called what
pleiotropty
76
what gene is responsible for sex determination
sry gene found on the y chromosome, means males who have the y chromosomes will develop male sex characteristics
77
what causes Hunington's disease
mutation in the HTT gene- causes buiolding blocks of DNA to repeat many more times than they normally do
it's hereditary
78
what causes down syndrom
trisomy 21- each cell has three copies of chromosome 21
79
what causes cru di chat
missing piece of chromosome 5- most cases occur in development of egg or sperm, but some cases occur when a parent passes a different, rearranged for of the chromosome to their child
80
what is amniocentesis
prenatal test by removing a small sample of amiotic fluid -- can be used to diagnose chromosomal conditions, genetic disorders
81
Hersey/Chase experiment
labeled phage's DNA with radioactive phosphorous and its protein coat with radioactive sulfur, Showed that the DNA represented the genetic material responsible for the inheritance of traits
82
what are the rungs of the helix are composed of
nitrogenous base pairs
83
the DNA backbone is held together by what type of bonds, and what carbons in the sugar are involved in these bonds
phosphodiester-- covalent, 5' carbon to 3' caron
84
why is new dna synthesized in the 5' to 3' direction
the enzyme responsible for building the DNA chain (DNA polymerase) can only add new nucleotides to the 3' hydrozyl group of the existing strand
85
What happens when a nucleotide is added to a growing strand of DNA? (What bonds are formed? Does it require ATP? What enzymes are needed?)
Phosphodiester bond formed between the nucleotide and growing strand of DNA, no— gets its energy from phosphate groups when breaking phosphate bonds within the nucleotide itself, needs DNA polymerase
86
what does primase do
enzyme that synthesizes RNA primers, which are short RNA sequences called primers
87
DNA polymerase I
in prokaryotic DNA replciation, support repair of damaged Dna, but also contributes to connecting Okazaki fragments
88
what does DNA polymerase III do
primary enxyme complex involved in the prokaryotic DNA replication- elongates DNA chains during bacterial chromosomal DNA replication
89
single stranded binding protein
binds to single strand of DNA near the replication fork
90
DNA ligase
enxyme that joins DNA strands together by forming phosphodiester bonds
91
how does DNA excision repair repair thymine dimers
Recognizes the distortion caused by the dimmer in the DNA helix, then cuts the DNA background on either size of the dimmer to excise the damaged section,, allowing a dna polymerase to fill in the gap with new nucleotides, finally sealing the nick with DNA ligase
92
Why is there an “end” problem with the lagging strand? What helps to protect the ends of the chromosomes? What enzyme is found in some cells to prevent this problem?
DNA polymerase can only add nucleotides in the 5’ to the 3’ direction, meaning it cannot fully replicate the very ends of the linear chromosomes on the lagging strand, leading to a gradual shortening with each replication cycle; telomeres are the protective structures at chromosomes end that prevent this issue, and the enzyme telomerase is found in some cells to extend these telomere res and counteract the shortening, thus preventing the loss of important genetic info.
At very end of chromosome, there isn’t enough space to add a primer for the last Okazaki fragment
93
What enzyme is responsible for synthesizing mRNA? In what direction does it synthesize the mRNA?
RNA polymerase synthesizes in 5’ to 3’ direction
94
What are the 3 stages of transcription?
initiation, elongation, and termination
95
what happens in initiation of transcription
binding of RNA polymerase and local unwinding of DNA
96
what happens in elongation stage of transcription
nucleotides are added to the 3' end of the growing RNA strand
97
what happens during transcription termination
the newly synthesized RNA strand is released
98
what is the TATA box, and where is it found
found in promoter region of eukaryotes in the core promoter. it acts as a sgnal for where transcription should begin, usually around 25-30 base pairs upstream of the trascription start site, marks the location where RNA polymerase should bind
99
what is meant by 5' UTR and 3' UTR
untranslated regions of messenger RNA-- influences mRNA stability and translation efficiency
100
what are splicesomes composed of
smll nuclear RNAs called small nuclear ribonucleoprotein particles (snRNPs)
101
what are 3 stages of translation
initiation, elongation, termination
102
initiation in translation
small subunit on mRNA binding site is joined by large subunit; aminoacyl tRNA binds
103
elongation of translation
ribosome moves along the mRNA extending the protein by shifting from peptidyl tRNA to aminoacyl tRNA
104
termination of translation
peptuide chain is released and ribosome dissociates from mRNA
105
what does aminoacyl-tRNA transferase do
attaches amino acids to tRNA molecules
106
what takes place at 3 different tRNA binding sites
enters at A, p is where polypeptide chain is attached to new amino acid, and E is where it exits
107
what is a polyribosome
cluster of ribosomes attached to a single mRNA molecule, allowing for the simultaneous tranlation of that mRNA into multiple protein copies, significantly increasing the protein synthesis within a cell
108
how is the translation of proteins destined for secretion different from those that will be used in teh cell
secreted proteins start their translation on the free ribosomes in the cytoplasm, but then are recognized by a signal sequence at their N-terminus, which directs the ribosome complex to the ER
109
what is meant by charging tRNA
process of attaching a specific amino acid to its corresponding tRNA molecule-- basically activating the amino acid-- aka amino acid activation
110
what is an operon
a group of genes that are transcibed together and controlled y a single promoter
111
describe the trp operon
cluster of genes in bacteria that code for enxymes necesary to synthesize the amino acid tryptophan, it is concered a repressible operon, it is turned on by default when tryptophan is needed and not readily available in teh environment.
regulated by trp represson
112
lac operon
— for using lactose instead of glucose— expresssed when lack of glucose, is inducible— only expressed when lactose is present
Usually turned off (repressed) but can be turned on
113
What effect does histone acetylation have on gene expression?
Histone acetylation activates gene expression — weaken the interaction between the histones and the negatively charged DNA, leading to a looser chromatin structure, so easier to promote transcription
114
what affect does methylation have on gene expression
slows or stops it
115
what role do transcription factors play in gene expression
Transcription factors are a broader category of proteins that bind to DNA to regulate gene expression,, including both activators and repressors.
Binds to dna to promote or inhibit the recruitment of RNA polymerase
116
what role do activators play in gene expression
Activators are proteins that bind to enhancer sequences on DNA— recruit other proteins like RNA polymerase complex to the promoter region, initiating transcription. Can be regulated by external signals, allowing for dynamic control of gene expression
117
what is a microRNA, and what does it do
Small, non-coding RNA molecule that plays a crucial role in regulating gene. Expression by binding to mRNA and inhibiting its translation into protein, effectively controlling the amount of specific protein produced within a cell
