ISCI Test 2

Gene

Gene

A section of DNA that contains instructions for building a protein

Genotype

Genetic makeup

Phenotype

Physical appearance (genotype + environment)

Eukaryotes

Nucleus, packaged as chromosomes (linear)

Histones

DNA wrapped around proteins

How many chromosomes (each) that most cells have?

2 (Two)

Diploid

Contains two sets of chromosomes

How many chromosomes do humans have?

46

Autosomes

Chromosomes 1-22

Sex chromosomes

Chromosome 23 (males XY, females XX)

Watson and Crick

Figured out that DNA was a double helix

Franklin

Took the famous X-Ray of DNA, which led Watson and Crick to their discovery

What is DNA Replication?

Semi-Conservative model (makes an exact duplicate)

DNA Replication

-Replication begins at a specific site -Topoisomerase- "relaxes" the strands (releases the supercoil, makes it look like a ladder) -Helicase- separates the strands (opens the helix) -the replication fork is created

Origin of Replication

Where the double stranded DNA unwinds and separates

Primase

Synthesizes a short RNA sequence (what happens first)

DNA Polymerase

Adds new DNA nucleotides to the 3' end of the primer (makes a DNA Polymer)

5'-3'

Can only work in one direction, and runs opposite of each other (2 strands of DNA are anti-parallel)

Leading Strand

Template strand where nucleotides are added from 5' to 3' (moves toward the replication fork)

Lagging Strand

-At replication fork, primase adds RNA primer -moves away from the replication fork -a discontinuous replication (making Okazaki fragments) -many RNA primers are made, but ultimately replaced by DNA

Central Dogma

DNA-->RNA-->Protein

Transcription

The gene's sequence is copied from DNA to a middleman molecule called mRNA

Transcription in order

1. Needs to open the helix by mRNA polymerase and bind to a starting point called the promoter cite

2. Transcribe

3. Terminate-where it pops off

4. Cap and tail (5 prime cap and 3 prime poly a tail)

Expressing Exons

Cutting out the introns, the non-coding proteins

Translation

Converts information carried my mRNA into functional proteins

Translation Cont.

-starts in the cytoplasm

1. Free amino acids

2. Ribosomal subunits (in eukaryotes, can be found in ER OR cytoplasm)

3. tRNA

4. mRNA is included as well

tRNA

t(transfer)RNA-molecules to read mRNA and translate that message from a sequence of bases into a protein

AUG

The start codon

UGA, UAA, and UAG

ALL are stop codons

Translation Steps

1. Recognize and initiate protein building (the START sequence)

2. Elongate

3. Terminate

Translation

The first tRNA will come into the P cite (always be a thymine)

The others are going to the A cite (the original animo will jump off the first one and attach to the second) E-Exit P-Primary A-All others

Mutations

When the sequence of nucleotides in an organism's DNA is changed

Where can mutations occur?

gamete-producing cells and non-sex cells (example: skin cells can cause skin cancer)

Point Mutation

Change of one base pair (one base pair is substituted for another, accidentality putting one instead of the other)

Frameshift Mutation

Base pair are inserted/deleted (causing a shift in the frame)

can be VERY dangerous

Chromosomal Aberrations

entire sections of a chromosome are altered -deletion of an entire section of DNA -Relocation of a gene within a chromosome -duplication of genes

Spontaneous Mutation

Mutations arise by accident as long strands of DNA are duplicating themselves (freak accident usually happening in DNA replication)

Radiation-induced Mutation

Ionizing radiation has enough energy to disrupt atomic structure by removing bound electrons (example: UV rays from the sun, can be absorbed by certain bases in DNA and cause them to rearrange bonds)

Chemical-induced mutation

chemicals can also react with the atoms in DNA molecules and induce mutations.

Meiosis

Replication for "private part" cells

Where does meiosis take place?

Gonads

Meiosis Division I: The Homologues Separate, moving homologues chromosomes

P1: Crossing over happens! M1: line up in the middle of the cell A1: Homologues are pulled apart and move to either side of the cell T1: makes a set of sister chromatids

Meiosis Division II: Separating Sister Chromatids

PII: no crossing over MII: moving the sister chromatid AII: sister chromatids move to opposite sides of the cell TII: makes four haploid cells (all together)

Mendel's Laws

1. Each individual organism possesses two alleles encoding a trait 2)Alleles separate when gamets are formed (Independent Assortment)

2. Alleles separate in equal proportions

Alleles

Different versions of a gene

Independent Assortment (Mendel's Second Law)

Alleles at different loci separate independently

Dominant

Trait masks the effect of a recessive trait when an individual carries both the dominant and the recessive versions

Homozygous

Inherits the same two alleles for a gene

Heterozygous

inherits a different allele from each parent