Genetics Ultimate Final Review

Intro Genetics Final Review

Aristotle

Aristotle

Believed semen shaped life through “vital heat”

Leeuwenhoek

First observed living cells in 1600s

Preformation

Imagined a homonuculus inside sperm

Epigenesis

Current accepted concept of development

Lamarck

theory of “use and disuse”

Weismann

Cut tails off mice, found that after 22 generations there was no affect on tails

Darwin

Galapagos finches

Mendel

Pea plants

Garrod

First mendelian trait in humans: Alkaptonuria

Morgan

Discovered sex-linkage

Franklin and Wilkins

X-ray crystalography

Watson and Crick

Double helix model

Khorana and Nirenberg

Genetic code

Independent Probability Equation
And

Multiply probabilities

Mutually Exclusive Events

Or

Add probabilities together

3^n

Number of genotypes possible assuming 2 alleles at each gene

Variance

Distribution around the mean

P

Variation among phenotypes

G

Variation due to genotypes

E

Variation due to environment

P = G + E

Variation among phenotypes is due to both genotype and environmental variations

Vp = Vg + Ve

Population variance is caused by both the genotype and environmental variance.

H2 = Vg/Vp

Broad sense heritability

Ve Average

Environmental variance is the average of P1, P2, and F1

Recombination Frequency

Number of Recombinants/Total number of Gametes

Genetic Distance

Equal to recombination frequency

Cis Chromosomes

Dominant and recessive alleles are on the same chromosome

Trans Chromosomes

Dominant and recessive alleles are on opposite chromosomes

Testicular determining factor

Mammalian determination of sex.

SRY gene

What leads to male development.

Genic Balance

Drosophila Sex Mechanism

Aneuploidy

Addition or loss of chromosomes less than an entire set

Trisomy 21

Down syndrome

Trisomy 13

Patau Syndrome
Cleft lip, lowset ears

50% fatality

Trisomy 18

Edward Syndrome

Clenched fists at birth

Rocker bottom feet

Monosomy

Singular chromosomes.

Lethal in utero when of the autosomes, however monosomy of X can survive.

Turner Syndrome

Monosomy X

Short stature, low hairline, poor brest development, fold of skin on back of neck

Female

Triplo X

Not associated with phenotype malformations, but have been found to have mild retardation

Klinefelter Syndrome

XXY

Hypogonadism, azoospermia, low testosterone, sexual dysfunction, mild retardation

XYY Syndrome

Taller than average, chance at more acne

Chromosomal Deletion

Loss of a piece of chromosome.

Terminal Deletion

Loss from an end of a chromosome

Interstitial Deletion

Loss from within a chromsoome

Cri-du-chat Syndrome

5p Deletion/Partial Monosomy

High pitched cry, severe mental retardation

Chromosomal Duplication

Double copy of piece of chromosome

7q12.23 Duplication

Broad forehead, straight eyebrows
Mental Retardatio

Reciprocal Translocation

Exchange of pieces by non-homologous chromosomes

Robertsonian Translocation

Fusion of two chromosomes

Paracentric Inversion

Inversion not including centromere

Pericentric inversion

Inversion including centromere

Angelman Syndrome

15q del from mother, normal 15 father

Mental retardation, hyperactivity, speech impairment, light hair and skin, happy disposition

Prader-Willi Syndrome

15q del from father, normal 15 mother

Obesity, overactive eating, hypogonadism, mild retardation, reduced muscle tone

Polyploid

More than two sets of chromosomes (3N,4N,5N). Fatal in humans but relatively common in plants. Used in commercial agriculture to yield larger crops.

Allopolyploid

Polyploid from two different species.

Satellite DNA

Relatively short sequences repeating many thousands of times in tandem. They are mostly found at centromeres or telomeres.

Moderately Repetitive DNA

Microsatellites (one or two bp repeated many times) or VNTR (short repeats of a few to few dozen bases). Can include some genes, an example of which are ribosomal RNA genes.

Sine

>500bp and present in more than 50,000 copies in humans

Line

5,000bp and present in more than 100,000 copies in humans.

Heterochromatin

DNA that highly coils composed of mostly repetitive DNA. Are centromeres and telomeres and replicate later in S phase.

Euchromatin

Less coiled and mosly unique DNA. Contain most of the genes and replicate early on.

Eukaryotic Chromosome

Composed of chromatin

Have DNA, histone proteins, non-histone proteins

Eukaryotic Chromosome Structure

DNA molecules tightly coiled around proteins called histones, forming a complex called chromatin. Chromatin further condenses to form chromosomes during cell division. Eukaryotic chromosomes have a linear structure and contain genes responsible for genetic information.

Nucleosome

Basic unit of DNA packaging in eukaryotes. Consists of DNA wrapped around a core of histone proteins. Helps condense DNA into a compact structure, allowing it to fit inside the nucleus. Plays a role in regulating gene expression and protecting DNA from damage.

Histone Proteins

Proteins that help organize and package DNA in eukaryotic cells. They are responsible for the structure and compaction of chromatin, the complex of DNA and proteins. They play a crucial role in gene regulation and DNA replication by controlling access to DNA. There are five main types: H1, H2A, H2B, H3, and H4. They form the core of the nucleosome, which is the basic unit of chromatin. Can undergo modifications, such as acetylation and methylation, which can affect gene expression.

Prokaryotic DNA

Circular, double-stranded molecule that contains the organism's genetic information. It is typically smaller and less complex than eukaryotic DNA. Plays a crucial role in cell replication, gene expression, and adaptation to the environment.

Cot Curves

Measure the rate of DNA reassociation to determine genome complexity. Steep curve indicates repetitive sequences, while a shallow curve suggests unique sequences.

S phase

The phase which DNA synthesis takes place

DNA Replication Steps

1. Initiation: DNA unwinds and helicase separates the double helix.

2. Priming: Primase synthesizes RNA primers to start replication.

3. Elongation: DNA polymerase adds nucleotides to the growing strand.

4. Proofreading: DNA polymerase checks for errors and corrects them.

5. Termination: Replication ends when polymerase reaches the end of the DNA molecule.

6. Ligation: DNA ligase seals any gaps in the newly synthesized strands.

Replication fork

Structure formed during DNA replication where the double helix unwinds and new strands are synthesized. It consists of a leading and lagging strand, with DNA polymerase enzymes working in opposite directions.

DNA Polymerase III

Links DNA Nucleotides

Primase

Creates primer which is needed to provide 3’ end for DNA polymerase to elongate strand

Okazaki fragments

Short DNA fragments synthesized on the lagging strand during DNA replication. They are later joined by DNA ligase to form a continuous strand.

Replication bubble

A region of unwound DNA during DNA replication. It forms when the double helix is separated, and replication occurs in both directions. It expands as DNA is replicated, allowing multiple replication forks to work simultaneously. There may be multiple in eukaryotes, which eventually grow into each other to produce two complete double helices.

DNA Polymerase I

Removes primers and leaves gaps that are then filled in. Also links DNA nucleotides in the gap

Telomerase

Enzyme that maintains the length of telomeres, which are protective caps at the ends of chromosomes. It adds repetitive DNA sequences to prevent loss of genetic information during cell division.

DNA polymerase II, IV, and V

Aid in mutation repair.

Transcription

The process in which an RNA molecule is synthesized from a DNA template by RNA polymerase. It involves initiation, elongation, and termination stages. During initiation, RNA polymerase binds to the promoter region of the DNA. Elongation occurs as RNA polymerase moves along the DNA template, synthesizing the RNA molecule. Termination happens when RNA polymerase reaches a termination signal, releasing the RNA transcript. This process is crucial for gene expression and protein synthesis.

RNA polymerase

Enzyme responsible for synthesizing RNA from a DNA template during transcription. It initiates transcription by binding to a specific DNA sequence called the promoter, then unwinds the DNA double helix and adds complementary RNA nucleotides to form an RNA molecule. Essential for gene expression and protein synthesis.

Initiation of prokaryotic transcription

Process where RNA polymerase binds to the promoter region of DNA, forming a closed complex. It then unwinds the DNA double helix, creating an open complex. RNA polymerase synthesizes a complementary RNA strand using the template DNA strand. Transcription initiation is the first step in gene expression

Eukaryotic Transcription

The process where DNA is converted into RNA in eukaryotic cells. It involves the binding of RNA polymerase to the promoter region of a gene, followed by the unwinding of DNA and the synthesis of RNA using a complementary strand.

Types of eukaryotic RNA polymerase

Transcription termination

The process in which RNA polymerase stops synthesizing RNA and detaches from the DNA template. It occurs when a specific termination signal is reached, leading to the release of the newly synthesized RNA molecule.

Eukaryotic Processing

Modifications to RNA after completing transcription. Cap 5’ end, clip conserved region on 3’ end, add polyA tail, remove introns and join exons.

Before this: pre-mRNA

After this: mature mRNA

Introns and Exons

Non-coding regions of DNA that are transcribed but not translated into protein.

And

Coding regions of DNA that are transcribed and translated into protein.

Splicing mechanisms

Process in which introns are removed and exons are joined together to form a mature mRNA molecule during gene expression. Two main types:

1) Exon skipping, where one or more exons are excluded from the final mRNA transcript.

2) Intron retention, where one or more introns are not removed and remain in the mature mRNA.

Ensures proper protein synthesis by determining the sequence of exons included in the mRNA.

Codons

Three nucleotides which are interpreted into one amino acid

Wobble Hypothesis

There is more than one codon for many amino acids.

Mature mRNA sequence

The final version of messenger RNA (mRNA) that has undergone post-transcriptional modifications, including the removal of introns and addition of a 5' cap and 3' poly-A tail. It contains the coding sequence (exons) that will be translated into a protein by the ribosomes.

Universality of Code

Genetic messages transferred from one organism to another results in the same same interpreted polypeptide

mRNA

Coded message from the DNA

Ribosome

Site where translation takes place

tRNA

Interprets mRNA code and brings in amino acids

Translation Initiation

Ribosome assembles on the mRNA, with the start codon.

Translation Elongation

Amino acids are added to the growing polypeptide chain, guided by the mRNA codons.

Translation Termination

Ribosome reaches a stop codon, releasing the completed protein.

Post-translational Modifications

Folding, cleavage, and chemical modifications that may occur to form final protein product

DNA Translation

Process where the genetic information in mRNA is used to synthesize proteins. It occurs in the ribosomes and involves three main steps: initiation, elongation, and termination. In initiation, the ribosome binds to the mRNA and starts reading the codons. During elongation, amino acids are added to the growing polypeptide chain based on the codons. Termination occurs when a stop codon is reached, and the protein is released.

Polysome

Multiple ribosomes translating a single mRNA molecule

Prokaryotic Transcription and Translation

Occur simultaneously within cytoplasm.

Polycistronic mRNA

A type of messenger RNA that contains multiple coding sequences, or genes, arranged in tandem. Found in prokaryotes, it allows for the simultaneous synthesis of multiple proteins from a single mRNA molecule. Enables efficient coordination of gene expression in prokaryotic cells.