Bio Test 4

Physical appearance

Genetic makeup

Unites of hereditary that effect an organisms traits

Partner chromosomes

alternative form of genes

Location of the gene on the chromosome

Expressed only if homogenous, not expressed if there is a dominant gene present

The expressed gene, homogenous or heterogenous

When a phenotype between the dominant and recessive gene are expressed 

Ex: pink rose when the dominant color is red and the recessive color is white

When two dominant genes are both expressed 

Ex: the erminette chicken

The same

Not the same

When there is only one allele (X-linked, for males, because there is only one X chromosome)

Before sexual reproduction occurs, the two alleles carried by an individual parent must become separated

Used to determine the possible genetic outcome of an offspring based on parents two genes

Crossing an individual of unknown genotype with an individual with known homozygous recessive genes to know if they have the recessive gene as well

Parent generation

First offspring generation

• 2nd generation of offspring from the P generation
• (Offspring of the F1 generation)

All the chromosomes inherited by the offspring would be exactly the same as the parents

When an intermediate phenotype is expressed

Ex: a pink rose when the dominant trait is red rose and the recessive trait is white rose

Codominance happens when both dominant genes are expressed at the same time 

Ex: black and white feathers make the erminette chicken

Genes are not able to determine personality or thoughts, and just because a gene is present does not mean it will ever be expressed

Carriers of genetic information in the cell

• Makes up chromosomes 
• Made of DNA and proteins

Begins chromosome packaging with proteins

Positively charged histones associate with negatively charged DNA

Inactive genes that are tightly packed in the chromatin

active genes that are loosely packed in the chromatin

• The histone proteins join together to form a molecule
• DNA then wraps around the histone molecules to make the nucleosome 
• They prevent the DNA from becoming tangled as it condenses in the chromatin

Chemical modifications (like sugars, methyl groups, acetyl groups) attach to the histone tails on the nucleosome and can turn genes on or off

• No cell division is occuring
• Cell is synthesizing materials and proteins that it needs

Chromosomes begin to condense

Chromosomes begin to line up in the middle of the cell

Microtubules pull each sides of the chromosomes apart and begin to separate them to each side

• Chromatins are separated to each side of the cell and cytokinesis begins
• Cleavage furrow forms as cell wall begins to form

Chromosomes separate into two daughter cells

• Division of the cell cytoplasm to form two cells 
• Often begins before mitosis is over

Cell division stops and the cell is permanently in this stage

• Proto-oncogens give the signal to the cell to stop dividing, which prevents the unregulated cell division that occurs in cancer cells
• Would tell the cell to stop dividing and return to the G1 state

They tell cells when to die and fix DNA mistakes that could lead to unprogrammed cell divisions that cause cancer

Two gametes meet to produce new life

Sex cells with half the required chromosomes of a normal cell

When an egg and sperm cell combine to form a single haploid cell

Contains one half of a homologous chromosome

Has both parts of the homologous chromosomes

When a cell has more than two chromosomes per pair

The genes can cross over during meiosis to form genes with new alleles from the original parent genes

• When homologous chromosomes lie side by side 
• During prophase 1

• The number of tetrads is equal to the haploid chromosome number 
• Ex: if the diploid number is four, there are two tetrads (total number of chromatids is 8)

When paired homologous chromosomes exchange genetic material

When crossing-over creates genetic diversity because the resulting genes are different from those of the parents genes

The cells inherit three chromosomes per gene which leads to death or genetic disease

• Number of purines equals the number of pyramidines
• Number of cytosine = number of guanines
• Number of adenine = number of thymines

• Discovered the spiral structure of the alpha helix
• DNA must consists of a multi stranded structure

• Created best viable model of DNA (double helix)
• The density of DNA means that is has structural limits

• Used X-Ray diffraction to determine the distances between the atoms of molecules arranged in a crystalline structure 
• Yields the orientation and placement of molecules in the DNA strand

• 5' is the head 
• 3' is the tail

Sugar- phosphate chains that contain base pairs of AT and GC

GC forms three hydrogen bonds while AT forms 2

• Only A and T can pair together 
• Only G and C can pair together

Guanine and Adenine

Cytosine and Thymine

• Purine: 
• contain 2 rings of atoms
• Wider than pyrimidines 

• Pyrimidines:
• contain 1 ring of atoms
• narrower than purines

Separates the hydrogen bonds and unwinds the DNA for replication

Bind to the single strand of DNA and stabilize them to prevent helix from reforming until the strands are replicated

Creates the RNA primer that starts a new strand of RNA

The enzymes that add nucleotides to the 3' end of the DNA template strand

• DNA polymerase can only add nucleotides to an already started strand, they cannot lay down the first nucleotide in a sequence
• RNA primer can lie down first nucleotide in the strand

They form in small groups because they cannot get too far away from the replication fork

always growing away from the replication fork

the place where both DNA strands replicate at the same time

• DNA can only be formed in the 5'--> 3' direction 
• the strand being copied is read in the 3'-->5' direction 
• The strand is being made backwards from the direction is it being read in

• DNA ploymerase extends the Okazagi fragment toward the 5' end of the synthesized fragment 
• DNA ligase links the 3' hydroxyl of one Okazaki fragment to the 5' phosphate of the DNA next to it

A DNA replication enzyme that lengthens DNA telomeres by adding repetitive nucleotide sequences

• A nuclease cuts out damaged DNA
• Dan polymerase adds the corrected nucleotides 
• Dan ligase seals the DNA strands back together

• mismatch repair
• enzymes recognize the incorrectly paired nucleotides
• DNA polymerase fills in the missing nucleotides 

• nucleotide excision repair 
• Nuclease removes damaged DNA 
• DNA polymerase adds the right nucleotides 
• DNA ligase seals the strand back together

The RNA primer that forms on the 5' end of the DNA strand cannot be replaced because there is no way to prime the 5' end of the replicating strand

• cancer cells 
• allows for the addition of random nucleotides to the DNA strand and is present in cells that divide infinite numbers of times

The telomere ends of the strand get shorter and that is a sign of early programmed cell death

They activate telomerase

Add acetyl groups to histone proteins

• HAT: Open up DNA strands that are wrapped around nucleosomes when the DNA needs to be replicated or transcribed 
• Activates gene expression

• HDAC: depressors of gene expression
• closes off histone proteins

Condenses the histone and removes acetyl groups from the histone proteins

Histones bind to DNA to neutralize their negative charge