Genetics Flashcards
(125 cards)
1
Q
Pyrimidines
A
Cytosine, Thymine, Uracil. These are all cyclic compounds and have Nitrogens and one Oxygen atom.
2
Q
DNA parts
A
Deoxyribonucleic acid. Doble stranded helix. Nitrogenous bases (ATGC) sugar phosphate backbone (deoxyribose)
3
Q
Purines
A
Adenine and Guanine. Bicyclic compounds with Nitrogens.
4
Q
What is a nucleotide made of?
A
Nucleotides contain a sugar [deoxyribose or ribose (RNA)] at the center, a phosphate and a nitrogenous base (CGTAU)
5
Q
What bonds to T (no T in RNA)
A
A
6
Q
What bonds to A
A
T (U in RNA)
7
Q
What bonds to C
A
G
8
Q
What Bonds to G
A
C
9
Q
What is a Gene?
A
A discrete Unit of inheritance
A sequence of DNA nucleotides that codes for a product (usually protein or RNA)
A specific DNA region on a chromosome.
10
Q
What is a Chromosome?
A
Thread-like structures made of protein and a (VERY LONG) single molecule of DNA.
11
Q
Chromosomes in Eukaryotic Vs Prokaryotic cells.
A
Eukaryotic: Multiple rod-like Chromosomes in the Nucleus
Prokaryotic: One Circular Chromosome found in the nucleoid region.
12
Q
What is a Locus?
A
A locus refers to a specific location on a chromosome. Could be an entire gene sequence down to a single base pair.
13
Q
What is an Allele?
A
One or multiple forms of a gene found at a locus.
14
Q
Phenotype?
A
An individual’s observable appearance = how the genotype “trait” is expressed or visualized.
15
Q
Genotype?
A
Specific alleles an individual possesses at a genetic locus
16
Q
Homozygote
A
The same alleles for a trait.
17
Q
Heterozygote
A
Different alleles for a trait.
18
Q
What is the Wild-Type?
A
The most commonly observed/ standard genotype or phenotype. (Commonly the dominant Allele.)
19
Q
What are Histone Proteins?
A
These are proteins used in helping package DNA within chromosomes. They limit accessibility of the DNA to proteins (enzymes) Directing gene Transcription. These help make up Chromatin.
20
Q
What is Chromatin?
A
Chromatin makes chromosomes and contains DNA and histone proteins.
21
Q
How many chromosome copies in a diploid cell
A
2 copies. EX: humans have 23 pairs of chromosomes; 46 chromosomes.
22
Q
What are homologs?
A
Chromosome pairs, these may carry different alleles of the same gene.
23
Q
How many copies of chromosomes in a haploid?
A
1 copy.
24
Q
What is a chromatid?
A
A chromatid is a half of a chromosome pair and is just one line. During anaphase and after of mitosis cells only have chromatids, which are still considered chromosomes when on their own.
25
Where are the telomeres on a chromosome?
The telomeres are the ends of the chromosomes
26
Where is the centromere on a chromosome and how is it related to the kinetochore?
The centromere is the constricted part of a chromosome, it's where the sister chromatids attach, the kinetochore protein forms here and the spindle microtubules attach.
27
What is a monohybrid cross?
A type of cross that only studies the outcomes of one loci. this could be eye color, size, texture etc.
28
What is a test cross?
Breeding the dominant homozygous phenotype with the recessive genotype.
29
What is a dihybrid cross?
A cross representing two loci. Ex: eye color and size, or Hair color & amount of pigment produced.
30
What is an autosomal gene?
A gene not located on the sex chromosomes.
31
What is genic sex determination?
Genes determine the sex, no sex chromosomes- sex becomes an autosomal trait.
32
in a male with XX-XY sex determination chromosome type. how many gametes will have an X sex chromosome after meiosis?
2 of the four gametes with receive the X chromosome, this is why sex in these situation is 50/50.
33
Difference between XX-XY and ZZ-ZW?
XX-Male carries the XY sex determining gene trait for male.
ZZ- The female carries the ZW sex determining gene trait for female.
34
How do sex chromosomes become homologous pairs?
They are not true homolog pairs and have pseudoautosomal regions commonly at the centromeres where they are "homologous".
The XY do not commonly have any cross over due to this and loci different regions.
35
What is an SRY gene?
Sex determining region on Y chromosome.
36
What is Aneuploidy?
Abnormal chromosome number.
Trisomy is more 2n+1
Monosomy is less 2n-1
Better tolerated on sex chromosomes, where as autosomally it is commonly fatal.
37
What is Hemizygous?
when there is only one allele present for a gene commonly in males on the X chromosome.
38
How are sex linked genes written?
Usually as a superscript on the X or Y chromosome.
39
Why are sex chromosome duplicates better tolerated in sex chromosomes than autosomal in Females?
In females one of the X chromosomes remains condensed and inactivated (Barr body)
40
How many barr bodies in XXX or XXY
2 in XXX and 1 in XXY
41
What causes mosaicism?
In females (XX) one X chromosome is deactivated into a barr body, this happens randomly early on in each cell. The same barr bodies will remain inactivated through cell division but are not the same in every starter cell.
42
What is incomplete dominance?
This is when two traits of the same dominance are on the same locus and represent at an intermediate form of the phenotypes. (EX: Red (R) White (W) RW = shows as pink
43
What is Co-dominance?
This is when two traits of the same dominance are on the same locus and represent both triaits. (EX: A blood type & B blood type= AB blood type- has both antigens.)
44
How to show ratio when a homozygous trait is lethal?
Get rid of the dead offspring and re-calc ratios.
EX: a cross gives yellow (YY) and gray (yy) fur: YY, Yy, Yy, yy. if YY is lethal the new ratio becomes out of three, not four.
45
What is penetrance?
The description of how/ if an individual expresses the phenotype of their genotype
EX: if an individual W/ a genetic variant does not develop features of the disorder, the condition is said to have reduced (or incomplete) penetrance.
46
What explains the reason that polydactyly is a dominant trait but is not the wild type in the population?
polydactyly has an incomplete penetrance and only 90% of people with the gene actually have polydactyly.
47
What is epistasis?
The interaction between genes at different loci (still independent.) This can mask the traits of other genes, EX: yellow labs are yellow because the ee gene code over-rides whatever the B/b genotype coded for and will always be a yellow lab.
48
What happens in cytoplasmic inheritance?
genes from the mitochondria or chloroplasts (plants). This usually only occurs from the mother due to the large egg having more cytoplasm than sperm. (Class Bivalvia will do this but the father also passes mtDNA to the male offsrping. so female- only mother's mtDNA & Male- Both parents mtDNA.
49
What is a karyotype?
The general appearance of the complete set of chromosomes. (Sizes, number, shape.)
50
Why does mosaicism cause patches?
Since the x chromosome that is inactivated into a barr body very early on, the same x chromosome stays inactivated in each cell divided from that cell.
51
A dog genotype for hind quarter dew claws, will always produced rear dew claws in dogs with this trait however, how developed/ pronounced the dew claws are varies (EX: just a stub Vs fully jointed.) What is this an example of?
The expressivity of a trait.
52
What is a sex influenced trait?
autosomal trait that will differ in it's dominance depending on the sex. EX: in male goats the allele for beards is dominant, and in females it is recessive.
53
An autosomal genotype that codes for extra plumage in chickens is only expressed in cocks, what is this type of trait called?
a sex-limited trait.
54
What is genetic maternal affect?
This is when the genotype of an individual does not determine the trait, but rather whatever the mothers genotype was. EX: The way a snails shell curls is either L or R, but the offspring will always match the mother's trait.
55
Family tree that outlines the inheritance of one or more characteristics.
Pedigree.
56
Person from whom the pedigree is initiated.
Proband.
57
What do the shapes mean on a pedigree?
Circle, square, colored in, blank?
Circle: Female.
Square: Male.
Colored in: Affected.
Blank: Un-affected.
58
Children in a pedigree are listed in what order?
From left to right in birth order.
59
What are the five inheritance patterns?
Autosomal Recessive
Autosomal Dominant
X-Linked recessive (Z-birds)
X-linked dominant
Y-linked (W-birds)
60
Pedigree shows equally affected males and females and skips some generations.
Inheritance pattern?
Autosomal Recessive
61
Pedigree shows equally affected males and females. unaffected people do not transmit the trait, and affected people have at least one affected parent.
Inheritance pattern?
Autosomal dominant.
62
Pedigree shows mostly males affected, affected males do not pass on the trait to sons. Can skip a generation.
X-linked Recessive.
(Male X chromosome comes from mother.)
63
how are X-linked recessive genes passed?
Males only inherit x chromosome from mother so if she is a carrier they can inherit the trait. With daughters they have two X chromosomes so, both parents would need to carry the trait for it to phenotypically show, other wise she may become just a carrier from the mother or father and can pass it to sons.
64
A pedigree shows affected males and females. Fathers pass the trait to all of the daughters and do not skip generations. All affected males have an affected mother. A heterozygous mother will affect half of her children and all if homozygous.
X-linked dominant.
65
A pedigree shows only men affected and all the sons of an affected father.
Y-linked.
66
What are two things we can mostly assume when looking at pedigrees?
Homozygous mutations are usually lethal.
Most people, unless evidence suggests otherwise, are homozygous wild type.
67
What are linked genes?
Genes that are physically close on the chromosomes and have specific inheritance patterns.
68
What is the difference between crossing over and recombination?
They both occur about the same time, but crossing over discusses homologous chromosomes pairing and exchanging genetic material and then recombination is the result of the new combination of alleles.
69
two parental gametes are (AA, BB) & and (aa,bb)?
The offspring are non-recombinant, what are their Gametes?
(AB, ab). (Same as the parents.)
70
Will majority of offspring usually be recombinant or not?
Majority offspring will usually be non-recombinant.
71
What is the max for recombination between two genes?
Recombination frequencies between two genes cannot exceed 50% due to random assortment being 50%, the closer the 50% the less likely the genes are linked and >30 means they are likely further than the % indicates.
72
What is polyploidy?
Organisms with more than two complete sets of chromosomes.
EX: Human Euploidy: 46 (2 sets), Polyploidy can cause 69 (3 sets) or 92 (4 sets) of chromosomes which tend to be fatal.
73
What is called when sister or homologous chromosomes fail to separate properly during meiosis 1 or 2?
Non-disjunction.
74
Peri-centric Vs para-centric chromosome issue/ mutation.
Pericentric happens around the centromere while paracentric does not involve the centormere.
75
What are Hela cells and what are they used for?
Cells collected from Henrietta lacks cervical cancer, non-consensual. They are/ were extremely beneficial to scientific discovery and experiments as they duplicated fast, had polyploidy, numerous chromosome mistakes and could rebuild telomere regions (immortal).
76
What are the 4 requirements of genetic material?
-Must store large amount of info.
-Replicated accurately.
-Encodes for phenotype
-Variability.
77
What is the structure of DNA?
Right handed Double helix DNA.
78
Name and info?
Type of pentose: Ribose (RNA) not as stable as DNA due to extra hydroxyl.
79
Name and info?
Type of pentose: Deoxyribose (DNA) H instead at the 2# carbon recognized by enzymes.
80
Purines, name the bases and what's different?
A & G They are bicyclic.
Two rings two bases; plus the letters almost look bicyclic.
81
Pyrimidines, name the bases and what's different?
C,T,U Only 1 ring /cyclic. (A can pair with U or T.)
| Think Triangle? only one ring?
82
What is a Nitrogenous base attached to a pentose called?
Nucleoside.
83
Name?
Phosphate group (-2) one of the O will attach to a nucleoside. Phosphate bind to the 5# carbon.
84
Phosphate + Nucleoside?
Nucleotide.
85
is DNA acidic or basic?
Both, the phosphate group is acidic (-2 charge) and the nucleoside is basic.
86
Name each group, the whole and number the carbons:
Nucleotide:
87
What is the backbone of DNA made of?
Phosphates and pentose sugars.
88
How are nucleotides connected?
Phosphodiester bonds.
89
How are adjacent (Matching) base pairs connected?
Hydrogen bonds.
90
What is the secondary DNA structure called a hairpin?
This is when the bases have a complimentary component within a single strand and will bond together forming what looks like a hair pin with a stem and sometimes a loop at the top of unpaired bases. This is especially common in RNA.
91
What is DNA methylation?
Addition of a methyl group to the nitrogenous base usually cytosine.
Bacteria use it to differentiate between origin and phage DNA (un-methylated.)
This can silence or repress the affected gene in eukaryotes.
92
Positive Vs. Negative Supercoiling?
What's most common?
(+): over rotated
(-): under rotated most common.
93
Enzymes that can add or remove a turn? Name and how?
Topoisomerases
By breaking the sugar-phosphate backbone rotating and then re-joining.
94
What are plasmids?
An extra circular double stranded genetics material separate from the chromosomes. Mostly in bacteria and provide advantages such as antibiotic resistance.
95
What is heterochromatin?
What are the two types?
parts of the DNA which remain highly condensed and are inaccessible to transcription. usually found near centromere and telomeres.
Constitutive: permanent: centrometeres/ telomeres.
Faculatative: changeable: x-inactivation.
96
What is euchromatin?
Chromatin that is able to de-condense and will only be condensed during cell division. Transcribable and contains most "genes"
97
What are histones?
Proteins that aid in DNA condensing, have many positively charged amino acid (+) "tails" and are attracted to the (-) DNA backbone.
98
What is a nucleosome?
"like a bead of DNA" The DNA wound around 8-sub units of histone protein.
99
What is a chromatosome?
Nucleosomes + locked in by H1Protein.
100
What connects nucleosomes/ Histone proteins?
Linker DNA.
101
What commonly de-condenses DNA?
Acetylation.
102
What commonly condenses DNA?
Methylation.
103
The overall pattern of chromatin modifications?
What is large factor affecting it?
Epi-genome, heavily influenced by environment.
104
Cells differentiate during development and will continue to produce the same type of cell,
What makes cells different when they have the same DNA?
Heritable chromatin structure
These cells differ in their expressivity of DNA to form specific tissues.
105
Type of Chromosome structure?
Telocentric
106
Type of Chromosome structure?
Acrocentric
107
Type of Chromosome structure?
Submetacentric
108
Type of Chromosome structure?
Metacentric
109
Name Three things about the centromere?
-Heterochromatin
-No genes, not defined DNA sequences.
-Likely defined by nucleosomes (Variant Histone CenH3 may alter chromatin structure and promote formation of kinetocore during pro-metaphase.)
110
What do the telomeres do?
Telomeres are protective "end-caps" of the Chromosomes they have repeating codes that do not contain genetic information. The lagging strand (5'-3') end is usually longer and will loop back around
(t-loop) to avoid detection from DNA repair.
The ends of chromosomes are not entirely replicated due to running out of space for primers with Okazaki fragments Since telomeres do not conain important genes this is okay and when the telomere runs out, the cell is no longer able to complete division (unless cancer)
111
What is senescence and what helps prevent this in certain cells like stem cells?
This is the stopping of cell division due to running out of sequences on the telomeres.
Telomerase can rebuild the telomeres to prevent this in stem cells.
(contains complementary coding 5'-AAT-CCC-3')
This will perform reverse transcriptase RNA--> DNA.
112
What Protein prevents Telomere ends from being repaired?
Shelterin
113
What is highly repetitive DNA called?
Satellite DNA
114
What is a single origin of replication point called?
Ori
115
What is the shape of bacteria Chromosomes and how many ori can it have?
Circular chromosomes and only one Ori- origin of replication.
116
What is the shape of eukaryotic Chromosomes and how many ori can it have?
Linear chromosomes and multiple ori at once.
117
What do 3' & 5' refer to?
The ends of DNA and how carbons are numbered in the deoxyribose sugar molecule. This gives the DNA a chain sort of direction.
118
in what direction is DNA synthesized?
Synthesis is only produced in the 5'-->3' direction due to it being anti-parallel and the DNA polymerase reading in the 3'-->5' direction. That is also how DNA is read & written. "Read up, Write down."
119
Are eukaryotic individual ori replication rates faster or slower than bacteria?
About 20x slower. There is much more info.
120
What synthesizes DNA by adding nucleotides to the 3' side?
DNA polymerases, catalyze the formation of a phosphodiester bond between the nucleotides.
121
DNA strand going towards the fork?
Leading strand. Reads 3'-->5' & synthesizes 5'-->3'
Continuous.
122
What are Okazaki fragments?
The fragmented DNA on the lagging strand cuase by it traveling in the 5'-->3' direction and synthesizing 3'-->5'. it points away from the fork and so as the fork moves away there is space that will need to be duplicated.
123
What breaks H bonds at each replication fork?
Helicase.
124
What relieves the supercoils ahead of the replication fork?
Gyrase
125
What joins the Okazaki fragments?
DNA Ligase
