Biology-Genetics Flashcards
define genotype:
Genetic makeup.
What are genes composed of? Where are genes located?
Made of DNA
Located on chromsomes.
Define phenotype:
Physical manifestation of genetic makeup.
What is Mendel’s first law?
Law of segregation.
Four principles of inheritance in Mendel’s 1st law:
1) genes have alleles (alternate forms)
2) there are 2 alleles for each trait- one from each parent.
3) two alleles separate in meiosis…gametes carry only one allele.
4) dominant allele is expressed; recessive allele is silent.
What is Mendel’s law of dominance?
Dominant allele appears in phenotype.
What is a monohybrid cross?
Studying only one trait.
Parental generation in monohybrid cross produces the…..
Filial generations.
What is the standard pattern if Mendelian inheritance?
Disappearance of recessive phenotype in F1 and it reappears in 25% of F2 generation.
What is done in a test cross?
Organism with dominant phenotype with unknown genotype is crossed with phenotypically recessive organism.
What does the appearance of the recessive allele in the progeny of a test cross indicate?
That the phenotypic dominant parent is genotypically heterozygous.
What is Mendel’s second law?
Law of independent assortment
What is dihybrid cross?
Parents differ in 2 traits.
What is a dihybrid cross requirement?
Genes must be on separate chromosomes and assort independently.
What is typical pattern of dihybrid cross between heterozygotes with independently assorting traits?
9:3:3:1
What is incomplete dominance?
Phenotype of heterozygotes is an intermediate of the homozygous parents. EX: pink flowers.
What is codominance?
More than 1 allele exists for a gene and more than one of them is dominant.
Example of codominance:
ABO blood groups. Can be A, B, O or AB blood type. AB blood type occurs because IA and IB are both dominant so their characteristics combine to form AB blood type
How many pars of autosomes do humans have?
22
Sex chromosomes for males and females:
Males: XY
Females: XX
Sex of human zygote is determined by what gamete?
Make gamete.
Examples of sex-linked recessive genes. Who do these occur in more often?
Color blindness and Hemophilia
More common in meh because there is no dominant allele to mask the gene.
How is it possible that sex-linked genes skip a generation?
Fathers cannot pass to son but if the daughter is a carrier their son may have the gene.
Why is drosophila melanogaster studied?
Fruit flies reproduce often, reproduce in large numbers, have few chromosomes (2N=8), have large chromosomes, have many mutations.
What impacts the expression of a gene?
Interaction of the environment and the genotype.
What is nondisjunction?
Failure of homologous chromosomes to separate during meiosis 1 OR
Failure of sister chromatid to separate during meiosis 2.
What are common results of nondisjunction?
Trisomy (Down’s syndrome-chromosome 21)
Monosomy
What are mutations?
Changes in DNA of a cell
What are mutations in somatic cells presented as?
Tumors
What happens to mutations in sex cells/gametes?
Passed to offspring
Most mutations occur in DNA regions that…
Don’t code for proteins…silent.
What induce mutation?
Mutagenic agents.
Examples of mutagenic agents:
Cosmic rays, X-rays, uv rays, and colchicine (inhibits spindle formation=polyploidy), mustard gas
Define mutation:
Permanent change in DNA sequence of gene that may or may not alter the AA sequence of protein.
What is PKU?
Phenylketonuria. Inability to produce enzyme to metabolize phenylalanine…..phenylpyruvic avid builds up.
What is sickle-cell anemia?
RBCs are crescent shaped because they contain defective hemoglobin. Less O2 is carried.
What mutation causes sickle cell anemia?
Valine is substituted for glutamic acid because of a single base pair substitution in hemoglobin gene
DNA of valine:
DNA of glutamic acid:
Valine= GUA or GUG
Glutamic acid= GAA or GAG
Genes are composed of:
DNA
DNA contains:
Genetic info coded in base pairs
DNA self-replication is the basis of:
Heredity
Basic unit of DNA:
Nucleotide
Components of a nucleotide:
Deoxyribose (sugar)
Phosphate group
Nitrogenous base
Two types of nitrogenous bases in DNA:
Purines and pyrimidines
What are the DNA purines?
Adenine and guanine
What are the DNA pyrimidines?
Cytosine and thymine.
CUT the PY
Cytosine Uracil and Thymine are pyrimidines
PUR As Gold
Purines are Adenine and Guanine
In the DNA helix, is the sugar-phosphate chain or the bases on the inside?
Bases are on the inside of the helix.
T forms …..hydrogen bonds with ….
2 hydrogen bonds with A
G always forms …..hydrogen bonds with…..
2 hydrogen bonds with C
The more G/C content, the more….
Tightly bound the DNA strands
What enzymes unwind DNA?
Helicase and gyrase enzymes
In DNA replication, what end does the RNA primer start on?
5’ end of new strand
Replication occurs on the ……direction
5’ to 3’
What does lagging strand do?
Adds nucleotides in Okazaki fragments
Why is DNA replication semiconservation?
DNA acts as template for synthesis of 2 daughter strands.
How many amino acids are there?
20
What is transcription?
DNA code is read to produce mRNA transcripts.
What is a codon?
Triplet codes on mRNA transcripts
Is the genetic code universal for all organisms?
Yes
T or F. Most amino acids have more than one codon specifying them.
True.
What is degeneracy of genetic code?
The fact that there are synonyms in the genetic code.
What is the difference between RNA and DNA?
RNA has ribose instead of deoxyribose
It contains uracil and not thymine
Single stranded
Where is RNA found?
Nucleus and cytoplasm
What does mRNA do?
Carries complement of DNA sequence from nucleus to ribosomes where proteins are made.
T Or F. mRNA is the complementary code of DNA.
True.
Is mRNA monocistronic in eukaryotes or prokaryotes?
Eukaryotes….codes for one polypeptide. (It is polycistronic in prokaryotes.)
What does tRNA do?
Brings AAs to ribosomes during protein synthesis.
What does rRNA do?
Structural component of ribosomes.
Where is rRNA made?
Nucleolus
What is the most abundant type of RNA?
rRNA. Ribosomal RNA.
What is transcription?
Process in which Info coded in base DNA sequence is turned in mRNA.
3 mains parts of transcription:
Initiation
Elongation
Termination
What happens in initiation of transcription?
RNA polymerase (adds RNA nucleotides) must recognize TATA box sequence were transcription should begin.
What happens in the elongation phase of transcription?
RNA polymers adds to the growing RNA transcript in the 5’ to 3’ direction.
When does transcription terminate?
RNA polymerase recognize sequence on new transcripts (ex: hairpin loop in prokaryotes)
Is complete mRNA transcript made from transcription in prokaryotes or eukaryotes?
Prokaryotes. In eukaryotes hnRNA still needs post-translational processing.
What must be done to hnRNA before it can be translated?
Remove introns (no gene code)
Splice together exons (gene sequence)
Protect transcript with 5’ cap and poly A tail.
What is translation?
mRNA codons are translated into AA sequence.
Where does translation occur?
Cytoplasm.
What does translation involve?
tRNA, ribosomes, mRNA, AAs, enzymes and proteins.
tRNA has two abilities:
RecogniZes AAs
Recognizes mRNA codon
Structure of tRNA:
- 3 nucleotide sequence anticodon that is complementary to a mRNA codon.
- AA attachment site
What is an aminoacyl-tRNA synthetase?
Enzyme with active site to bind AA and tRNA.
What are the 3 binding sites of ribosomes?
1 for mRNA
2 for tRNA
What is the p and a site of a ribosome?
Binding sites for tRNA.
P site binds to tRNA attached to polypeptide chain.
A site binds to incoming aminoacyl-tRNA complex.
Ribosome scans mRNA until it finds what start codon?
AUG
Methionine-tRNA has what anticodon?
3’-UAC-5’
Concurrent action of translocation=
Ribosomes advances 3 nucleotides along mRNA in 5 to 3 direction. *uncharged tRNA from P sure is expelled, peptidyl-tRNA from A site moves into P site. The a site is then ready for the next amino-acyl tRNA for the next codon.
When does polypeptide synthesis stop?
When mRNA termination codons enter A site: UAA, UAG or UGA.
What bonds create secondary protein structure?
Disulfide bonds
T or F. DNA is found in chloroplasts, mitochondria and other cytoplasmic bodies.
T.
What are plasmids?
Cytoplasmic rings of DNA containing genes….responsible for drug resistance.
Bacterial genome is single circle chromosome located where?
Nucleiod region
What are episomes?
Plasmids capable of integrating into bacterial genome.
In what direction does replication of the bacterial chromosome occur?
Both directions.
Bacteria cells reproduce with….
Binary fission.
How can bacteria increase genetic variance?
Transformation
Conjugation
Transduction
What is transformation in bacterial reproduction?
Foreign plasmid is incorporated in chromosome via recombination
What is conjugation in bacterial reproduction?
Sexual mating: transfer of genetic material between two bacteria that are temporarily joined.
What forms in conjugation of bacteria?
Conjugation bridge. Sex factors are transferred from male to female.
What is the common sex factor studied in bacteria?
F factor in E. coli.
F+ cells replicate f factor give to F- recipients.
Bacteria with the sex factor integrated into genome are called…..
Hfr cells
High Frequency of Recombination.
What is transduction in bacterial replicaton?
Fragments of bacterial chromosome package into viral progeny made during infection. These can then infect other bacteria
What allows bacteria to control their metabolism?
Transcription/regulation of gene expression
Regulation of transcription is directed by….
An operon.
What is an operon made of?
Structural genes(DNA that code for proteins), operator gene(repressor binding site), promoter gene(initial binding site for RNA polymerase).
What is an inductive system?
Require presence of a substance (an inducer) for transcription.
What are repressible systems?
Constantly transcribing unless corepressor is present to inhibit transcription.
RNA polymerase binds to the promoter——>
Structural genes are transcribed.
Repressor binds to operator——>
Structural genes NOT transcribed
Inducer binds to repressor—–>
No binding to operator—–>structural genes transcribed
What is a bacteriophage?
Virus that infects it’s host bacterium by attaching to it, drilling a hole and injecting it’s DNA while it’s protein coat remains attaches to cell wall.
What kind of cycles do bacteriophage enter once inside it’s host?
Lytic or lysogenic cycles
What is a Lytic cycle?
Bacteriophage enters hosts and the bacteria cell lyses and releases new virions that can infect other bacteria.
What are virulent bacteriophages?
Replicate by Lytic cycles and kill host cells
What is a plague in respect to bacteriophages?
Clearing in played culture corresponding to area of lysed bacteria
What is lysogenic cycle?
Bacteriophage doesn’t lysed and integrates into genome in a harmless way (prophage) until it reemergence and enters Lytic cycle.
Gel electrophoresis when is agarose gel used?
To separate DNA molecules of different sequence lengths.
Gel electrophoresis when are synthetic polymers gels like polyacrylamide used?
To separate protons of various AA lengths.
What is blotting and when is it used?
Used to preserve the sample. Used to detect molecules.
What does southern blotting allow for?
Specific DNA sequence.
What is northern blotting used for?
Detection of RNA.
What is western blotting used for?
Detection of specific proteins.
How can DNA amplification be done?
PCR (polymerase chain reaction)
3 steps of PCR:
Denaturation of DNA
Annealing- primers attach to single stranded templates at the start of the delisted sequence.
Primer extension- attach bases contemplate to template.
How can genes be amplified with gene cloning?
DNA is connected to vectors (self-replication phases) via DNA ligase. It is inserted into bacteria through transformation. Bacteria produces identical copies of DNA
What is the most popular DNA sequencing method?
Chain termination method.
What does the chain termination method use?
ddNTPs (dideoxynucleotides- modified to prevent addition). Separate single stranded result with electrophoresis.
How is DNA tested for diseases?
Restriction fragment length polymorphisms (RFLPS)
How does RFLP work?
Restriction enzymes bind and but DNA at specific sequences. Allows for identifying the patterns for disease and specify genes involved.
