Genetics And Molecular Biology Flashcards
1
Q
What is genetics?
A
Study of the inheritance of observable traits from one generation to the next, and their effect on population and species
2
Q
what is molecular biology?
A
The study of the molecular processes involved in the transfer of genetic information from phenotype to genotype
3
Q
what is a genotype?
A
Organism’s genetic makeup, genetic info contained in genes
4
Q
What is a phenotype?
A
organism’s physical traits, and biochemical traits
5
Q
How are phenotype and genotype determined?
A
Genotype determines phenotype
6
Q
What is the p telomere and q telomere?
A
cap of a chromosome
7
Q
What is the long arm of a chromosome called?
A
q arm
8
Q
What is the short arm of a chromosome called?
A
p arm
9
Q
What is a homologous chromosome?
Additionally, what makes them different?
A
Not identical, same size and shape, exist in G1
- They are arranged with the same gene sequences, however these genes may differ (different alleles)
10
Q
What is a locus?
A
Specific place along length of a chromosome where a gene is located (ex: eye colour)
11
Q
what is an allele?
A
Alternative versions of same gene ex: red eye allele and white eye allele
12
Q
What are sister chromatids?
A
Identical, two DNA strands, copies for mitosis, AKA mitotic chromosomes,
13
Q
What are somatic cells?
A
Have two sets of homologous chromosomes, they are diploid (2n chromosomes)
14
Q
What are sex cells?
A
Have on set of homologous chromosomes, haploid (n chromosomes)
15
Q
What is a human karyotype?
A
Display of condensed chromosomes arranged in pairs, identification of chromosomal abnormalities
16
Q
How is DNA organized?
A
DNA is complexed with proteins called histones, DNA+histones form nucleosomes, which coil into fibres, which undergo loops and scaffolding to become chromatid
17
Q
What is the purpose of mitosis?
A
To ensure an exact copy of parent cell’s DNA is passed on to the 2 new daughter cells.
18
Q
What are some forms of asexual reproduction?
A
Budding: plant has sprouts
Fragmentation: taking pieces of a plant and planting them
BOTH form identical clones!
19
Q
What are gametes?
A
Egg and sperm cell contain a single basic complement (haploid) of chromosomes
20
Q
What is fertilization?
A
Fusion of haploid chromosomes to form a new diploid cell, producing zygote
21
Q
What is meiosis?
A
Cellular process of reducing diploid cell to a haploid to produce sex cells
22
Q
what is meiosis useful for?
A
Ensuring variation in each haploid cell
23
Q
What happens in meiosis 1?
A
prophase, metaphase, anaphase, telophase = homologue chromosomes separate into sister chromatids
24
Q
What happens in meiosis 2
A
Prophase, Metaphase, anaphase, telophase = sister chromatics split into 4 genetically varied haploid cells, (crossing over occurs, each haploid has one copy of each chromosome)
25
Why is sex necessary when there is asexual reproduction?
For variation
26
What is hybridization?
Crossing of two true-breeding varieties
27
What did Mendel say about variations in genes?
Alternative version of a gene accounts for variation, for each character two copies of a gene are inherited (one from each parent, dominant expressed)
28
What is Mendells first law?
Two alleles for a heritable character segregate during gamete formation and end up in different gametes
29
What does heterozygous mean?
Organism with two different alleles for a character
30
What does homozygous mean?
Organism with a pair of identical alleles
31
What is a dihybrid cross?
32
What is Mendel's second law?
independent assortment of genes: during gamete formation a pair of alleles for one gene wills segregate independently of a pair of alleles for another gene
33
What are some deviations from Mendel's law?
1) some traits are not on nuclear chromosomes
2) traits on some chromosomes: genes near each other said to be linked
3) traits carried on sex chromosomes
4) Incomplete dominance
5) lethal recessive
6) Co dominance and multiple alleles
34
what is incomplete dominance?
a 'mix', red and white flowers form pink flowers: incomplete dominance
35
What is multiple alleles and co dominance??
Another deviation from Mendell's law
36
What are lethal alleles?
recessive gene results in death
37
What are the 3 classifications of genetic disorders?
Multifactorial, chromosome, single gene
38
What are congenital malformations?
A multifactorial disease
ex: Congenital Cleft lip, heart defects, neural tube defect
incidence: variable bit with 1/250-600 with ethnic variation
39
What is cancer?
A multifactorial disease
Some forms of genetic disorders, multiple curses including genetic predisposition
Incidence: greater than 1/3, exclusive of skin cancer
40
What is coronary artery disease?
A multifactorial disease: multiple causes including genetic predisposition
incidence: variable, up to 1/15 in Western population
41
What are some examples of chromosomal or cytogenetic disorders?
Down syndrome and XYY syndrome
42
What condition causes Down syndrome?
- Trisomy 21, an additional chromosome 21
Incidence: 1/800
43
What condition is it called when there is an extra y?
XYY syndrome,
incidence: 1/1000 males
44
What is nondisjunction?
Chromosomes don't split during meiosis
Gives rise to monosomic and trisomes
45
What is a monosomic?
Lacks a single copy of chromosome
46
What is a trisomic?
Carry an additional copy of a chromosome
47
Are giesma stain the same as genes?
Giesma stains are NOT the same as genes, they are simply a nucleic acid stains that attach to A-T bonds. There are way more genes on a chromosome than Giesma stains.
48
What are sex chromosome disorders?
Include a misalignment of X/Y chromosomes
49
What is Klinefelter syndrome?
47 chromosomes, XXY, sterile, male with female body characteristics
50
What is Turner syndrome?
45 chromosomes, one X chromosomes, sterile, female, short stature/immature sex organs
51
What is XXX syndrome?
47 chromosomes, XXX, fertile, associated with learning difficulties
52
What is XYY syndrome?
47 chromosomes, fertile, associated with behavioural difficulties
53
What are single gene disorders?
- caused by mutant genes, mutant gene may be present on only one chromosome of a homologous pair (dominant) or on both chromosomes (recessive) to exhibit the degree
-usually obvious pattern of inheritance in a pedigree
- most defects are rare
54
What are some examples of single gene disorders?
-cystic fibrosis, Huntington's, Duchenne muscular dystrophy, sucks cell anemia
55
What is cystic fibrosis?
A common autosomal recessive disease,
| single gene disorder
56
What is Huntington's disease?
Autosomal dominant, late onset
- higher in some small populations
57
What is Duchenne muscular Dystrophy?
Common x-linked recessive disorders
- rare in females
58
What is sickle cell anemia?
Autosomal recessive. common in equatorial Africa
59
What are the 3 traits about human pedigrees?
1) Autosomal or sex linked?
2) Dominant or recessive trait?
3) caused by a single gene or more than one gene?
60
How do you determine if a pedigree is autosomal or sex linked?
A sex linked trait will predominantly be seen in males
61
How do you determine if a pedigree is dominant or recessive?
dominant: each parent also afflicted
62
How do you determine if a trait is caused by a single gene or more than one gene?
Single gene: heterozygous parents have 25% of offspring affected
63
How awesome is Lilly?
SUPER AWESOME
64
What is the series of steps of evidence for DNA?
1. Isolation of the nuclein: miescher
2. transformation of bacteria: Griffith
3. Purification of DNA: Avery
4. Hershey-chase experiment
5. X-ray differentiation: Rosalind Franklin
6. DNA model: Watson and crick
7. Semi constructive DNA model: meselson and stahl
8. Molecular components of DNA replication: kornberg
65
Describe Friedrich Miescher's experiment
- Isolated a new molecule from the nucleus: the nuclein (now known as the DNA)
- Made up of carbon, hydrogen, oxygen, nitrogen, and phosphorus
-Unique ratio of phosphorus to nitrogen
66
Describe Griffith's experiment
- Griffith wanted to form a vaccine against the causative agent of pneumonia. Wish to kill the bacteria by heat to make a vaccine.
- A harmless R-strain of D.pneumonia produced rough shaped colonies
- A virulent S-strain of bacterium produced smooth shaped colonies
- Griffith used both strains in his experimental work
67
What was discovered from Griffiths experiment?
The ability to cause infection has been transferred from dead S-cells to harmless R-cells
R cells had been 'transformed'
- did not know what the transformative cause was
68
Describe the mouse aspect of Griffith's experiment
Griffith used S strain and killed the mouse
Griffith used R strain and the mouse survived
Griffith used dead s strain and the mouse lived
Griffith combined dead S strain with live R strain and the mouse died (transformation)
69
Why are S cells smooth?
They are covered by a sugar 'capsule' which allows the bacteria to stay in the body
70
Describe the goal of Averys experiment and his conclusion
Purification of DNA: in order to determine what aspect of cell (protein or DNA) which causes the transformation
- used lysate with different enzymes (to remove, protein, nucleic acids) to determine which is responsible for the transformation
- since the transforming principle was not the sugar coating or protein then it must be on of the nucleic acids
71
Describe the procedure of Avery's experiment
Avery preformed his invitro experiments in test tubes
1) Mixed lysate with R cells, become S cells
2) Mixed lysate with enzyme which eliminates the sugar coating - Still forms S cells
3) Mixed lysate with enzyme which removed protein - Still forms S cells
4) Mixed lysate with alcohol to purify nucleic acids
- removed the RNA - Still s cells
- removed DNA- R strain (the DNA is responsible for transformation!)
| conclusion: DNA carries genetic information
72
What is the goal of the Hershey-Chase experiment?
Uses radioactivity (and colour) and phages which kill bacteria to determine the only DNA is required for genetic info and not protein
73
How does a batch of phages with sulphur look?
Mix the sulphur (linked with proteins) with radioactive phages (solution is pink)
- the phages release their DNA into the bacteria after blended
-Centrifuge so it forms a solid
- the liquid solution is bright pink indicating that the radioactive protein is NOT involved in genetic material transfer
Reveals that DNA=Genes
74
What is the chemical structure of DNA?
The nucleotide is the building block of DNA, formed of a 5 carbon sugar group
- phosphate group on 5' and a base on 1' carbon of deoxyribose
-Nucleotides join to form polymer of DNA strand
75
What is the difference between ribose and deoxyribose?
Deoxyribose has one less oxygen
76
Which bonds join nucleotides together?
Joined by phosphodiester bonds in 5' to 3' antiparallel
77
How are bases bonded?
| Also, what binds bases together as well as the phosphate sugar backbone?
- A-T, G-C
- Bases are joined by covalent hydrogen bonds
- Sugar phosphate backbones are held together by phosphodiester bonds
78
Describe X-ray diffraction
Rosalind Franklin and her X-ray crystallography diffraction photo showing the helical structure of the DNA molecule
79
What is the Watson and Crick DNA model?
Watson and crick 'fit' the base pairing within the diameter specified by franklin's x-ray (purine matches with pyrimidine)
80
Describe the meselson and stahl model
3 different DNA models proposed
1) Conservative model
2) semiconservative model
3) dispersive model
81
How does the meselson and stahl model work?
Heavy and light isotopes separate the DNA, the resulting bars were only consistent with semi conservative model
82
What are the two requirements for DNA synthesis?
- DNA replication by any DNA polymerase needs to be initited from a double-stranded segment of nuclide acid (either DNA:DNA or DNA:RNA)
-synthesis can only happen in the 5' to 3' direction
83
What are the types of proteins associated with DNA replication?
(5) Helicase, single stranded binding protein, primate, DNA polymerase III, DNA ligase
84
What is the function of Helicase?
Unwinds parental double helix at replication forks
- 'unzipping' enzyme
85
What is the function of single-stranded binding protein?
Binds to an stabilizes single stranded DNA until it is used as template
- keeps the strands separate while the DNA is replicated
86
What is primase?
Synthesizes an RNA primer at 5' end of leading strand and at 5' end of each Okazaki fragment of lagging strand
- tells polymerase 'where to start'
87
What is DNA polymerase III?
Using parental DNA as a template, synthesizes new DNA strand by adding nucleotides to RNA primer or a pre-existing DNA strand
- preforms the actual replication!
88
What is the result of DNA replication? Whose experiment corroborates this?
Two semi-conservative strands of DNA
- meselson and stalls experiment proves this model
89
What is ligase?
Ligase 'glues' the Okazaki fragments back together
90
What are Okazaki fragments?
Since polymerase can only synthesize in 5' to 3' direction the leading strand is continues as the DNA is unwound
- the lagging strand runs anti parallel and therefore builds 'backwards' in the opposite direction of the unwinding: the polymerase must keep moving back to the start, resulting in fragments
91
What are the steps of genetic coding?
DNA--> RNA---> protein (transcription and translation)
92
What 'code' results in an amino acid?
one codon from an RNA strand (set of 3 letters) codes for one amino acid
93
What is a promoter and a terminator?
codons which code for start (AUG) and stop
94
What are the steps of transcription?
1) recognition of promoter by RNA polymerase (occurs before transcription)
2) initiation of transcription
3) elongation of transcription
4) termination of transcription and production of mature messenger RNA
95
What happens in the recognition stage of transcription?
The RNA polymerase binds to the DNA strand after the promoter
96
What happens in the initiation stage of transcription?
After RNA polymerase binds to the promoter, DNA strands unwind, polymerase initiates RNA synthesis at start point
97
What happens in the elongation stage of transcription?
Polymerase moves down in 5' to 3' direction, unwinding DNA and elongating RNA. DNA strands reform into double helix after polymerase has passed.
* note: polymerase codes the DNA sequence into an RNA sequence ie: T becomes U
98
What happens in the termination stage of transcription?
Eventually RNA transcript is released, polymerase detaches, mature mRNA strand created
99
What are the 3 types of RNA used in transcription?
Messenger rna (mRNA)
Transfer RNA (tRNA)
Ribosomal RNA (rRNA)
100
What is messenger RNA?
A polymer of nucleotides that contain information to be converted by translation into a polypeptide
101
What is transfer RNA?
Transports specific amino acids to the ribosome, the protein synthesizing complex
102
What is ribosomal RNA?
Complexed with proteins to form ribosome
103
What is the sequence for a start codon?
AKA promotor: AUG
104
What is the sequence for a stop codon?
AKA terminator: UAA, UAG, UGA
105
What are the steps of translation?
1) initiation of translation
2) elongation of translation
3) Termination of translation
106
What occurs during initiation of translation?
Small ribosome subunit binds to molecule of mRNA
Arrival of a large ribosomal subunit complete the initiation complex
107
What occurs during elongation of translation?
Recognizes codon, binds and creates a peptide chain
108
What occurs during termination of translation?
Ribosome reaches a stop codon on mRNA, release factor promotes hydrolysis, two ribosomal subunits and other components dissociate
109
What kind of energy is required for protein synthesis?
ATP or GTP
110
What is a multifactorial disease?
A disease that comes from the issues of combination of genes as well as environmental factors
111
Why is the cell at meiosis II in prophase already considered Haploid?
Because they are sister chromatids ie: already haploid
112
How many gene sequences does the lac operon have?
3
113
How many gene sequences does the tryptophan open have?
5. trp A,B,C,D,E,F
114
What is an inducible operon?
An operon whose expression increases quantitatively in response to an enhancer (ex: lactose increases production)
115
What is a repressible operon?
An operon in which transcription of the gene is inhibited by a particular substance.
116
What is the role of the 5 genes in tryptophan operons?
5 subunits make up enzymes for tryptophan synthesis (don't need to make more trp because there is enough)
117
What is the difference between co-dominance and incomplete dominance?
Co-dominance: Traits from both alleles are expressed
Incomplete dominance: Traits from both alleles 'mix'
118
How does tryptophan operon work?
On the DNA sequence, the regulatory protein (made by the regulatory gene) does not bind to the promoter so the tryptophan can be synthesized. once there is enough, however, it becomes a 'negative feedback loop and binds to the protein to inhibit the open properly.
- Called a repressible operon
119
How does the lacoperon work?
- On the DNA molecule, the protein does inhibit the synthesis of lactose enzymes. once there is enough lactose, it binds to the protein and stops it from binding to the promoter (conformational change) so it can synthesize the enzymes to break down lactose
- This is called an induced operon
120
What are allosteric proteins?
Proteins which have two sites: regulatory site and an active site. Regulatory proteins are an allosteric protein.
