Genetics

meristic traiits

Phenotypes in which quantitative measurements are provided in whole numbers

Threshold traits

quantitative traits distinguished by number of discreate phenotypic classes (Has a small number of discreate classes)

Multigene hypothesis

Phenotype controlled by many genes which contribute in quantitative ways

Additive allele

Contributes something

Nonadditive allele

Contributes nothing

What happens when there are more additive alleles

There are more dominant appearances

How can phenotypics traits that show continuous variation be quantified

Through measuring, weight, etc...

1/4n

ratio of F_z expressing either extreme polygene

Antl

Number of distinct categories observed

Covariance

variation common to both traits

COV_xy

the sum of [(x,-x)(y,-y)]/n-1

Adaptation hypothesis

Implies phage & bacteria are essential to acquisition of immunity

Spontaneous mutation

Random mutation not induced by mutagenic agent

Luana & Delbruck

Fluctuation test provided first convincing evidence of bacteria

minimal medium

Contains only inorganic ions & organic carbon source

Prototroph

Strain capable of growing on minimal medium (Autotrophs are unable to do this)

Genetic recombination

Provides basis for chromosome mapping

Horizontal gene transfer

Nonreproductive transfer of genetic information from one species to another

Vertical gene transfer

Reproductive transfer

Conjugation

Info from one bacteria is transferred to another

F pilus

On bacteria cells posessing an F factor, a filament like projection that plays role in conjugation

Flexibility factor

Confers ability to donate part of chromosome during conjugation

To serve as a genetic material it must have

Replication
Storage of information
Expression of information
variation by mutation

Replication

Meiosis

Storage of information

requires molecule to act as repository for genetic info that may or may not be expressed

expression of information

information flow of transcription & translation

Proplasts

Bacteria with cell wall removed

Retrovirus

Virus using RNA or genetic material; employs enzyme reverse transcript use in life cycle

Mendel in populations

Frequencies of Alleles in populations permit the prediction of specific genotypic and phenotypic frequencies

Definition of Population:

A population is a group of individuals from the same species that can interbreed.

Subpopulation:

A local population that may enjoy/suffer partial mating isolation in relation to the total population.

A Gene Pool

all of the alleles present in population.

What does the Hardy Weinberg Equilibrium model?

the Number of Alleles That are Available in a Population to Contribute to Any Genotype.

The Hardy-Weinberg Equation:

A Mathematical Bridge Between Allele Frequencies and Genotypic Frequencies.

The Hardy–Weinberg model assumes

-there is an equal rate of survival and reproduction (no selection)
-no new alleles arise or are created by mutation
-there is no migration into or out of the population
-the population is infinitely large
-random mating occurs

What are three additional important conditions of the Hardy-Weinberg Law

-Dominant traits do not necessarily increase from one generation to
the next
-Genetic variability can be maintained
-By knowing the frequency of just one genotype, the frequencies of other
genotypes can be calculated

How can you calculate frequencies of multiple alleles?

Through the use of the Hardy-Weinberg equation if you add more variables

Example of how the Hardy-Weinberg Law can be applied to humans

analysis of susceptibility to HIV-1 infection based on
the CCR5 gene, which encodes a protein called CCR5, which is
also a receptor for strains of HIV-1

Violations of Hardy Weinberg expectations are often called

Microevolutions

Microevolutions

Evolution within a species, within a population seen with changes in allelic OR genotypic OR phenotypic frequency

What is an indicator of a genotype without changes to P and Q?

The population is Not Free Breeding, Inbreeding.

What is an indicator of changes in p and q?

1. Mutation, Adds New A or a Alleles.
2. Small Population Size Leads to Genetic Drift.
3. Migration, New Subpopulation Enters From Outside.
4. Natural/Darwinian Selection.
5. Neutral Evolution.

Mutation Rate:

Usually the Frequency, per Generation, That A Changes into a For a Given Population.

Genetic Drift and Natural Selection:

Both Cause Large Changes in p and q.

Genetic Drift:

Change in Allele Frequencies in a Population Due Solely to Sampling Error. Most Pronounced in Small Populations.

What does Genetic Drift often lead to?

“Fixation” of an Allele, Eliminating Polymorphism in a Population

Shifty Peaks:

Darwinian Selection Alters Variation in a Population by Causing a Relative Loss or Gain of Individuals With Specific Phenotypes (and Associated Genotypes)

How Does Selection Act:

By Increasing or Decreasing the Probability that a Phenotype (and Genotype) will Produce Offspring

Darwinian Fitness:

The Relative Likelihood that a Phenotype Will Survive to Maturity and Contribute Progeny to the Next Generation.

Reproductive Success:

The Average Number of Offspring Produced by Any Individual Genotype. Important in All Calculations of Darwinian Fitness.

Using Relative Fitness to Modify Allele Frequencies in the Hardy Weinberg Equation. example

____

To Determine Frequencies After One Generation of Selection We Must Again Make This Equation = 1.

____

Using a Data Set to Calculate Mean Fitness and Frequencies After One Generation of Darwinian Selection.

______

For W = .799, After One Generation of Selection, What Are the New Genotypic Frequencies?

____

After One Generation of Selection in Favor of the Heterozygote How Have the Genotypic Frequencies Changed.

Lowered Fitness of AA and aa Results in an Increase in Individuals that are Aa in the Next Generation, Because Homozygotes are Less Able to Produce Progeny.

phylogenies

evolutionary histories

Example of phylogenetic trees

-Branches represent lineages over time
-Groups that consist of an ancestral species and all its descendants
are called monophyletic groups

The Neanderthal Genome Project has resulted in a draft sequence of the Neanderthal genome

-The genome contains 3.2 billion base pairs, the same as ours
-It is 99.7 percent similar to our genome
-Both the Neanderthal genome and our genome are 98.8 percent similar to that of the chimpanzee

Biological Informatics:

DNA is the Cell’s Hard Drive But that Means it Must be Copied with Each Cell Division

What are the Three modes of DNA replication?

-Conservative
-Original helix is conserved and two newly synthesized strands come together

-Semiconservative
-Each replicated DNA molecule consists of one "old" strand and one new strand

-Dispersive
-Parental strands are dispersed into two new double helices

Two possible models of DNA replication

Semiconservative
Semi discontinuous

What happens when the strands of the helix are unwound

it creates a replication fork

DNA polymerase

catalyzes DNA synthesis and requires a DNA template, a complemented primer with a free 3’OH, and all four deoxyribonucleoside triphosphates (dNTPs)

What are things that DNA polymerases I, II, and III can and can't do?

can elongate an existing DNA strand (called a primer)
cannot initiate DNA synthesis

How many subunits is DNA polymerase III made up of?

10

There are seven key issues that must be resolved during DNA
replication:

-Unwinding of the helix
-Reducing increased coiling generated during unwinding
-Synthesis of a primer for initiation
-Discontinuous synthesis of the second strand
-Removal of the RNA primers
-Joining of the gap-filling DNA to the adjacent strand
-Proofreading

What binds to the origin of replication and is responsible for
the initial steps in unwinding the helix

DnaA

Outline of DNA Replication

_____

Gyrase/Topoisomerase:

Relaxes Helix Above the Replication Fork, Helicase Melts the DNA Double Helix

SSB:

Prevents Template Strands from Resealing

Primosome:

Produces the RNA Primer

DNA Pol I

Eats Primers, Synthesizes Replacement DNA, 5’-3’ Exo, 5’-3’ Pol…Ligase: Seals the Nicks.

Eukaryotic DNA replication shares many features with
replication in bacteria

-Double-stranded DNA unwound at replication origins
-Replication forks are formed
-Bidirectional snythesis creates leading and lagging strands
-Eukaryotic polymerases require four deoxyribonucleoside
triphosphates, a template, and a primer

However, eukaryotic DNA replication is more complex due to
several features of eukaryotic DNA:

-There is more DNA than prokaryotic cells
-The chromosomes are linear
-The DNA is complexed with proteins

Genetic recombination involves

-endonuclease nicking
-strand displacement and pairing with complement
-ligation
-branch migration
-duplex separation to generate the characteristic Holliday structure

What is Genetic exchange at equivalent positions along two chromosomes with substantial DNA sequence homology referred to as?

general, or homologous, recombination

Positive Supercoiling:

Addition of twists Tending To Overwind the DNA Helix. (Tends to Tighten the Helix)

Negative Supercoiling:

Addition of twists Tending to Underwind the DNA Helix. (Tends to Loosen the Helix)

What are chromatin?

Eukaryotic chromosomes are complexed into a nucleoprotein structure

Heterochromatin:

Highly Condensed and Tightly Compacted Regions of the Chromosome. Few or No Genes are Present.

Euchromatin:

Less Condensed Regions of Chromosomes, Home to Most of the Genes Found on Chromosomes.

What is Chromatin bound up in nucleosomes with?

positive charged proteins called histones or less positively charged nonhistones

The five main types of histones

H1
H2A
H2B
H3
H4

nucleosomes

linear array of spherical particles inside of chromatin fibers

Sequence Complexity:

Relative Proportions of DNA in an Organism That Show Similar or Disimilar Sequences. More Complex Sequences Have Fewer Repetitive Elements.

Highly Repetitive DNA:

DNA With Little or No Gene Coding Ability. No Genic Information. 100s-1000s of Copies.

Mid-Repetitive DNA:

DNA Encoding tRNA, rRNA, snRNA and Other Multi-Copy Genes. 10s-100s Copies.

Unique DNA:

Most Genes on the Chromosome. 1-10s Copies.

Bacterial Phenotypes are usually what?

growth, nutrition or drug resistance phenotypes

Selection

the growth of the organism under conditions in which only the phenotype of interest grows well, whereas the wild type does not.

Antibiotic Resistance

Allows bacteria to continue to infect hosts even under antibiotic treatment.

Phage Resistance

Allows bacteria to grow in viruses that would normally kill them.

What happens when the F factor is present,

the cell is able to form a sex pilus and serve as a donor of genetic information

what happens when During conjugation, a copy of the F factor is transferred from the F+ cell to the F- recipient,

it converts the recipient to the F+ state

what does An Hfr (high-frequency recombination) have?

the F factor integrated

An Hfr strain can donate genetic information to an F– cell, the recipient does not become F+

F+ x F- 🡪 recipient becomes F+ (low rate of recombination)

Hfr x F- 🡪 recipient remains F- (high rate of recombination)

What did Interrupted matings demonstrate in an Hfr strain

specific genes in an Hfr strain are transferred and recombined sooner than others

How is The chromosome of an Hfr strain transferred?

lineraly

how can The gene order and distance between genes be predicted

Time mapping

What is an F factor?

a Plasmid a self replicating “mini-chromosome” that can be transferred from bacteria to bacteria and replicated