Midterm #1 Flashcards
What is Mendel’s first law
- discrete units called genes
- have variants called alleles
- diploidy have 2 copies of the gene
- segregate independently (during meiosis)
- unite at random
What is the genotype ratio and phenotype ratio of a heterozygous cross for a single gene?
Génotype: 1:2:1
Phenotype: 3:1
What is the cross of 2 homozygous in single gene?
All heterozygous
What is the cross of 2 heterozygous?
3: 1 phenotype
1: 2:1 genotype
What is the cross of a homozygous recessive and heterozygous? In single genes?
1: 1 phenotype (50% Aa - 50% aa)
1: 1 genotype
What is mendels second law?
Différent gene combination assort independently in gamete formation and in fertilization (need to multiply probabilities of the genes independently)
In two genes - results of crossing 2 heterozygous genes?
9:3:3:1
In two genes, cross of 1 heterozygousand one homozygous? (Test cross)
1:1:1:1
What is a test cross?
To check if the parent is heterozygous, where the recessive will show up in the progeny
What is a dihybrid cross?
Two heterozygous genes crossing
Probability of two independent events occurring together is the product of their ____
Individual probabilities
Probability of A and B occurring is?
A x B
Probability of A or B occurring is
(P)A + (p)B
How many pairs of chromosomes do humans have?
23
22 autosomal - one sex one
What are the three types of centromeres?
Telocentric (at the end)
Afrocentric (close to end)
Meta centric (center)
What is a dyad? What is the individual chromosome called?
A chromosome pair attached at centromere
A chromatid
What are the stages of the life cycle?
Mitosis
G1
Synthesis
G2
What are the differences between meiosis and mitosis?
Meiosis:
- align from top to bottom where crossing over can occur
- 2 divisions
- results in 4 haploid gametes
Mitosis
- align left to right
- 1 division
- results in identical daughter cells as parents (diploid)
Know the stages of mitosis!!
1
Organelle chromosomes are inherited from
Material gametes
Do not exist in pairs and are similar to bacteria
Do not follow mendel’s 3:1 ratio
When there is a deviation from the 9331 or 1111 ratios ___
Suspect linkage of genes
How do you calculate the % recombinants?
Add all recombinants and divide by their sum
How do you calculate the interference?
1- observed cross over / expected cross over
What is the chi square test for?
Décide if a real data set matches the theoretical
What is the equation for chi square?
Sum of (Observed - Exp)power of 2 /expected
And look at degree of freedom (# of classes -1)
Table - cut off is 5%
Accept or reject the null hypothesis
What are linked genes?
Genes that are physically located on the same chromosomes and are therefore linked by the DNA between them
When given the % recombinant, you are given the___
Distance between the two genes (map unit)
When two genes are linked they ___ assort independently
Do not
But produce recombinant frequency of less than 50%
The further the distance between two genes…. the___
Most likely that a cross over will take place
What is a 3 point test cross?
To deduce if the 3 genes are linked and their orde r+ distance
Double recombinants will have the ___ sequence as parents?
The same
What is the difference in bacterial chromosomes?
Haploid Circular No nucleus or organelles Their genes is the phenotype Often uses e-coli
What are the three different classes of genes in bacteria?
1- resistance to antibiotics
2- requirement of nutrients (phototrophs/autotrophs)
3- ability to grown on compounds as sole carbon source
What s a phototroph?
Wild type that grows on Minimal medium
What is an auxotroph ?
Mutant that needs supplements or they will not grow
Bacteria mating is under the control of a___
Fertility factor
What is an épisome (plasmid)
Freely replicating circular piece of DNA
What is a high frequency recombinant factor?
Ability to promote a high frequency recombination by integrating in the recipient chromosomes
What is the incoming linear DNA called?
Exogenote
What is the recipient circular DNA called
Endogenote
How is an exogenote integrated?
By double cross overs
How can a gene order in bacteria be determined?
By the time it takes to transfer different genes to recipient strain
What are the different kinds of genetic information transfer in bacteria?
- Conjugation (plasmid + fertility factor)
- Transduction (with bacteriophages)
- Transformation
What is incomplete dominance?
When the phenotype of the heterozygous is intermediate between the two homozygotes
What is the ratio of a codominance?
1:2:1
What is recessive lethal alleles?
Recesssive homozygous causes death
An allele that affects to traits is called?
Pleiotropic
What is the one gene one polypeptide hypothesis?
Genes encode enzymes that process synthesis
What is a complement test?
Crossing two indi for different recessive mutations, if progeny is wild type (normal) they are said to be complemented
What is epistasis?
Allèles of one gene masks the facets of alleles of another gene
What is the ratio of recessive epistasis? Dominant?
9: 3:4
12: 3:1
What are the different gene interactions?
- complete dominant
- incomplete dominance
- co-dominance
- recessive lethal
- 3 or more allés of a single gene
- multiple genes that affect the same trait
- epistasis
When there are multiple allés for one gene, what ratios do we see?
3:1, 1:1, 1:2:1
What ratios do we see when multiple genes affect the same trait?
9:3:3:1
What is epistasis?
Individual will be white for c, no matter what the b gene says
What is the DNA molecule made up of?
- Nitrogenous base pairs - that attach by hydrogen bonding to each other (from different strands)
- Deoxyribose sugar
- phosphate groups
Does A = T or = G or = C
A=T
G=C
1-(G+C) = (A+T)
how does replication occur?
- Unwinding of DNA strands into two, that will become a template (Leading + landing strands)
- ## nucleotides are added from a pool of nucleotides (from
What enzyme unwinds the double helix?
Topoisomerase
What enzyme breaks hydrogen bonding of 2 strands
Helicase
What is a primer?
DNA or RNA
Synthesized by primase
Becomes the Okasaki fragment
What does DNA polymerase do?
Synthesize DNA
Central enzyme in replication
Fastest at replicating is POLIII
What direction does DNA polymerase move on leading strand?
5’ to 3’
What substrate is used to add nucleotide?
Triphosphate
What is the role of POL I?
To remove rna at 5’ end and fill gap
What enzyme joins adjacent fragments?
DNA ligand
Both POL I and III possess what that helps in proofreading?
Exonuclease - which serves as proofreading
POL I is primarily involved in DNA repair, removal and new synthesis
What is the difference between eukaryotic and prokaryotic organic or chromosomes replication
Eu - multiple origin
Pro - one origin
What is the Telomerase used for?
Helping te lagging strang synthesis which cannot proceed all the way to the tip.
It uses a primer - to add multiple copies of a single non coding sequence to the DNA at the chromosome tips.
What does a telomerase do?
Reverse transcription - fills terminal gaps
