Test 2 Flashcards
1
Q
incomplete dominance
A
a blend of the two phenotypes
2
Q
codominance
A
both phenotypes are expressed, no new phenotype
3
Q
lethal alleles
A
- dont evolve, no phenotype
4
Q
lethal recessive alleles
A
no phenotype for the recessive (3:0)
5
Q
lethal dominant alleles
A
Rare, since it usually results in death before reproduction (0:1)
6
Q
epistasis
A
when the expression of a gene is modified (masked, inhibited or suppressed) by the expression of one or more other genes.
7
Q
multiple alleles
A
- small differences in the DNA sequence of a gene which result in differences in the structure of the protein
- when a single gene is made up of 2+ alleles
8
Q
polygenetic inheritance
A
- several genes contribute to the overall phenotype of the trait (quantitative traits ; height, eye color, etc)
- many genes control a single trait
9
Q
what are sex-linked genes?
A
genes on the sex chromosomes (X,Y)
10
Q
what is the difference between the inheritance of a X-linked gene in a male and a female?
A
Females need to have the gene on both X chromosomes and males only need to have it on their only X
11
Q
where are the sex genes?
A
autosomes
12
Q
autosomal dominant
A
allele is dominant and carried on autosome
13
Q
autosomal recessive
A
allele is recessive and carried on autosome
14
Q
X-linked dominant
A
allele is dominant and carried on X chromosome
15
Q
X-linked recessive
A
allele is recessive and carried on X chromosome
16
Q
what does it mean if there is a skip in generation?
A
recessive
17
Q
if recessive and more men than women
A
probably X-linked, if not, probably autosomal
18
Q
what is the particularity in X-linked recessive?
A
affected mother always has affected sons
19
Q
what is the particularity in X-linked dominant?
A
affected father always has affected daughters
20
Q
what is the Mendelian pattern of blood type?
A
multiple alleles
21
Q
rhesus blood type
A
Rh+ is completely dominant over Rh-
22
Q
IM and IN blood type
A
codominance
23
Q
what is a testcross?
A
crossing the phenotypically dominant with a recessive homozygote to determine the genotype of individual one.
24
Q
what is the typical ratio for incomplete dominance in F2?
A
1:2:1 (2 of the new phenotype)
25
what is the typical f2 for codominance?
both phenotypes expressed, no new phenotype. Half will have both
26
what is the typical f2 ratio for lethal recessive allele?
3:0 (one is dead before showing phenotype)
27
what is the typical f2 ratio for lethal dominant allele?
0:1 (3 are dead)
28
what is the typical f2 ratio in epistasis?
9:3:4
29
what are the complementary base pairs in dna?
A-T, C-G
30
what are the complementary base pairs in rna?
A-U, C-G
31
how to perform transcription on an open reading frame?
transcription: from dna to rna with complementary base pairs (from start to stop)
translation: from rna to amino acids using table
32
missense mutations
- do not change reading frame
- alter the identity of one aa
- one base pair is different from normal
33
consequences of missense mutations on mRNA and protein
- an altered codon in the mRNA
- moderate to deleterious effects on protein (cannot function properly, since an aa is wrong)
34
nonsense mutation
- generates an early stop codon (premature termination)
- mutated base pair creates a stop codon
35
consequences of nonsense mutations
- stop codon created early in mRNA
- protein is truncated, not done, = severe effects on protein
36
silent mutations
- generate no change
- mutated base pair creates a changed codon but codes for same amino acid
37
consequences of silent mutations
- mRNA is different of one base pair
- protein is unchanged
38
frameshift mutation
- insertion/deletion of a base pair (DNA) causes reading frame to be off by one on mRNA
- aa altered due to frameshift
39
consequences of frameshift mutation
- reading frame off by one in mRNA
- rest of protein after mutation is changed
40
what are the SNPs?
missense, nonsense, silent, and framshift
41
what are the LCRs?
deletion, duplication, translocation, inversion
42
what is deletion? example
- deletion of a segment of DNA
- may cause severe problems if the missing segment contains genes that are essential for the normal development or cellular function
- ex: one deletion from human chromosome 5 leads to severe cognitive impairment and a malformed larynx = cri du chat
43
what is translocation? example
- a segment of DNA breaks from one chromosome and attaches to another nonhomologous chromosome
- Burkitt lymphoma (cancer) caused from translocation that moves a segment of chromosome 8 to chromosome 14
43
what is duplication? example
- a segment of DNA is duplicated
- can be harmful or beneficial, depending on the genes and alleles contained in duplicated genes
- ex: mammals have additional hemoglobin genes (beneficial) that come from duplication followed by mutation on duplicates
44
what is inversion? example
- a. chromosome segment breaks and reattaches to the same chromosome, but in reverse order
- important in evolution of plants and animals
- 5 of the chromosome pairs in humans show translocation and inversion not present in gorillas (helped us evolve more)
45
what does snp mean and how can it affect an organism?
- they affect only one gene
- single nucleotide polymorphism (not always one nucleotide, but only one gene)
46
what does lcr mean and how can it affect an organism?
- large chromosomal rearrangements
- affects many nucleotides
- creates a very large change in organism
47
what are the 3 steps of transcription?
initiation, elongation, termination
48
what happens in initiation of transcription?
-transcription factors bind to promoter and recruit RNA polymerase
- transcription can begin
49
what are transcription factors?
proteins that bind to DNA and regulate gene expression by promoting/supressing transcription
50
what is a promoter?
- TATA box
- attaches with RNA polymerase
- contains necessary proteins to initiate transcription
51
what is elongation in transcription?
- RNA polymerase 2 moves along DNA to unwind it and add new RNA nucleotides in 5' to 3'
- behind, DNA reforms double helix
- hybrid DNA-RNA dimer exists briefly
52
in which way does RNA polymerase read DNA?
5' to 3'
53
what is termination in transcription?
- RNA polymerase is released
- we now have a pre-mRNA that still needs to be processed (releasing introns)
54
what is RNA polymerase 1?
transcribes DNA to rRNA (ribosomal)
55
what is RNA polymerase 2?
transcribes protein coding genes (mRNA - messenger)
56
what is RNA polymerase 3?
transcribes DNA to tRNA (transfer - bring aa to ribosomes)
57
what is rRNA?
- ribosomal RNA
- in ribosomes and responsible for reading the order of aa and linking them together
- protein synthesis
58
what is mRNA?
- messenger RNA
- carry protein information out of nucleus to ribosomes
- contains protein info
59
what is tRNA?
- transfer RNA
- bind to mRNA by complementary bp
- at one end of tRNA: anticodon that pairs with codon (mRNA)
- other end: binds to aa to bring it
60
what is initiation in translation?
- start codon indicates beginning (reading frame)
- establish reading frame in mature mRNA (splicing done)
61
what is splicing?
- when pre-mRNA is processed
- exons stay, introns are spliced (released)
62
what is elongation in translation?
- uses aa instead of nucleotides
- A-site: tRNA with an attached aa bind to mRNA with anticodon/codon
- P-site: peptidyl transferase enzyme forms bond between aa (from P and A site) - N bonds with C, aa cleaved from tRNA, where polypeptide is forming
- E-site: empty tRNA exists
- A-site now free to receive next tRNA
63
which is the template strand?
3' to 5' (TAC)
64
which is the coding strand?
5' to 3' (ATG)
65
what is the start codon in coding strand?
ATG
65
what is the start codon on the template strand?
TAC
66
in which way is mRNA transcribed?
from 5' to 3'
66
in which way is translation written?
amino sequence in N to C direction
66
what must be done with an intron in an open reading frame?
RNA processing: deleting whole intron
67
what are polysomes and what do they do?
- a cluster of ribosomes traveling along the same mRNA strand
- simultaneous translation by multiple ribosomes increases the efficiency (more proteins produced in less time)
68
what are chaperones?
- proteins that assist/help the folding of large proteins
- make sure proteins are properly folded how they should be
69
what is the lac operon?
- an example of prokaryotic regulation
- inducible
70
what is an operon?
sequence of genes + a promoter and an operator involved in the same metabolic pathway
71
how does the repressor act when there is no lactose in the lac operon?
- the repressor is active and bonded with the operator, which prevents transcription
- no RNA polymerase can bind = no transcription
- when there is no lactose, there is no need to activate the genes that metabolize it (3).
72
how does the repressor act when there is lactose in the lac operon?
- even when there is no lactose, there is a basal level of the 3 gene products in the cell - they convert lactose to allolactose when it becomes present (with help of beta galactosidase)
- the allolactose binds to the repressor, which inactivates it, so it doesn't bind to the operator.
- transcription can occur
73
is the lac operon anabolic or catabolic?
catabolic: it produces enzymes that degrade lactose (produces energy)
74
is the trp operon anabolic or catabolic?
anabolic: it produces products used to manufacture tryptophan (consumes energy)
75
what is the trp operon?
- 5 trp genes necessary for tryptophan anabolism
- repressible
76
what happens when there is no tryptophan in the trp operon?
- need to make it
- trp repressor inactie = does not attach to operator = transcription occurs
- RNA polymerase is not stopped
77
what happens when there is tryptophan in the trp operon?
- no need to make it
- tryptophan binds to repressor, activating it, it binds to the operator and stops transcription
78
why are the trp and the lac operons negative gene regulators?
they are regulated by a repressor that turns off a gene expression when it binds to DNA
79
which lac operon gene codes for beta galactosidase and what is the function of beta galactosidase?
lac Z, it cleaves lactose
80
which lac operon gene is needed to allow lactose to enter E coli?
lac Y, it makes the cell permeable to lactose
81
what does lac I gene code for?
the repressor (protein)
82
what is the job of the promoter?
to bind with the RNA polymerase
83
what is the start codon in the coding strand?
ATG
84
what is the start codon in the template strand?
TAC
85
what are the stop codons in the coding strand?
TAA, TAG, TGA
86
what are the stop codons in the template strand
ATT, ATC, ACT
87
what are the stop codons in mRNA?
UAA, UAG, UGA
