Unites of hereditary that effect an organisms traits
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
Not the same
When there is only one allele (X-linked, for males, because there is only one X chromosome)
Principle of Segregation
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
First offspring generation
- 2nd generation of offspring from the P generation
- (Offspring of the F1 generation)
What happens if chromosomes do not independently sort?
All the chromosomes inherited by the offspring would be exactly the same as the parents
How is incomplete dominance inherited?
When an intermediate phenotype is expressed
Ex: a pink rose when the dominant trait is red rose and the recessive trait is white rose
How is codominance inherited?
Codominance happens when both dominant genes are expressed at the same time
Ex: black and white feathers make the erminette chicken
How would you respond to the statement "genes determine everything about a biological organism"
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
What is the role of histone proteins 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
How does histone packing effect gene expression?
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
What happens at the G0 phase?
Cell division stops and the cell is permanently in this stage
How do proto-oncogenes work to regulate cell division?
- 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
How do tumor suppressor genes work to control cell cycle progression?
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
How does meiosis produce gametes with unique gene combinations?
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
What happens if chromatids do not separate during meiosis?
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
James Watson and Francis Crick
- 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
What does 5' and 3' refer to in DNA?
- 5' is the head
- 3' is the tail
What are the structural components of the DNA molecule?
Sugar- phosphate chains that contain base pairs of AT and GC
What are GC basepairs stronger than At basepairs?
GC forms three hydrogen bonds while AT forms 2
What are the rules of base pairing?
- Only A and T can pair together
- Only G and C can pair together
What are the purine bases?
Guanine and Adenine
What are the pyrimidine bases?
Cytosine and Thymine
Compare and contrast the shape and size of pyrimidine bases and purine bases
- contain 2 rings of atoms
- Wider than pyrimidines
- contain 1 ring of atoms
- narrower than purines
Separates the hydrogen bonds and unwinds the DNA for replication
Single-strand binding proteins
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
Why must primes produce an RNA primer before DNA polymerase can build a new DNA 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
How do lagging strands form as they follow the replication fork?
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
How do DNA strands form in the opposite direction?
- 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
What is the role of DNA polymerase and DNA ligase in completing lagging strand synthesis?
- 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
How is DNA synthesis involved in DNA repair?
- A nuclease cuts out damaged DNA
- Dan polymerase adds the corrected nucleotides
- Dan ligase seals the DNA strands back together
Mismatch repair VS nucleotide excision repair
- 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
Why do linear DNA molecules get shorter with each cycle of DNA replication?
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
What cells contain high levels of Telomerase?
- cancer cells
- allows for the addition of random nucleotides to the DNA strand and is present in cells that divide infinite numbers of times
What is the consequence of chromosome shortening?
The telomere ends of the strand get shorter and that is a sign of early programmed cell death
How do cells get around chromosome shortening?
They activate telomerase
Add acetyl groups to histone proteins
What do HAT's and HDAC's do?
- 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
What does histone deacetylase do?
Condenses the histone and removes acetyl groups from the histone proteins
what is histone acetylation?
Histones bind to DNA to neutralize their negative charge