GENETICS Flashcards
Gene
a section of DNA that codes for a particular protein, heritable factor that controls specific characteristics
Allele:
Allele: an alternative version of the same gene
Chromosome
Chromosome: wound up DNA contained in the nucleus, made up of protein and DNA
Gene Locus:
Gene Locus: specific position of a gene on a chromosome
Genotype:
Genotype: the symbolic representation of the pair of alleles possessed by an organism
Phenotype:
Phenotype: The characteristics/traits of an organism expressed by a gene
Dominant Allele:
Dominant Allele: an allele that has the same effect on the phenotype, regardless with paired with the same allele or a different one (ALWAYS EXPRESSED IN PHENOTYPE)
Recessive Allele:
Recessive Allele: an allele that has an effect on the phenotype only when in homozygous state
Co-dominant Allele:
Co-dominant Allele: pair of alleles that both are expressed in the phenotype
Homozygous:
Homozygous: having two identical alleles of a gene
Heterozygous
Heterozygous: having two different alleles of a gene
Carrier:
Carrier: An individual with a recessive allele of a gene that does not affect the phenotype
Testcross:
Testcross: testing a suspected heterozygote by crossing with a known homozygous recessive
Tt x tt
Gregor Mendel’s Law of Inheritance
Gregor Mendel (1822-1884) created the three laws of inheritance Law of dominance → certain features dominant over others Law of segregation → homologous pairs separate during genetic formation Law of independent assortment → maternal + paternal chromosomes in homologous pairs line up randomly at the equator
Law of dominance
Law of dominance → certain features dominant over others
- dominant allele completely masks the effects of a recessive allele. A dominant allele produces the same phenotype in heterozygotes and in homozygotes
Law of segregation
Law of segregation → homologous pairs separate during genetic formation
- in diploid organisms, chromosome pairs (And their alleles) are separated into individual gametes (egg or sperm) to transmit genetic information to offspring
Law of independent assortment
Law of independent assortment → maternal + paternal chromosomes in homologous pairs line up randomly at the equator
- Alleles on different chromosomes are distributed randomly into gametes
Genetic code:
Genetic code: consists of A T C G, in CODONs (triplets)
- its universal
- codes for proteins
Cystic Fibrosis
Cystic Fibrosis is the mutation of the CFTR gene, which causes people to produce excessive mucus in organs (respiratory and digestive systems)
- deletion mutation: three nucleotides, ATC, are deleted. Therefore the amino acid phenylalanine is deleted.
effect:
The gene, ATC, codes for the protein pump which pumps salt through membranes. The protein pump’s shape is changed so it no longer functions. Where salt goes water follows, if salt can’t get through membranes neither will water for the most part. This heavily affects internal organs and the digestive system since water cannot get to them and they are not lubricated enough. When water is not carried into these areas food scrapes through the organs and thick mucus builds up in the trachea, resulting in a constant cough.
MUTATIONS:
MUTATIONS:
A mutation is a random, rare change in genetic material
Types: Deletion Substitution Insertion/Addition Can occur during DNA replication Can have negative AND positive effects on an organism's survival
Beneficial Mutations:
Beneficial Mutations: a mutation that provides an individual or species with a better chance for survival
example of a Beneficial Mutations:
- LRP5 gene helps immune system cells make a certain protein that acts as a receptor on their surface, people with a mutation in the LRP5 gene cannot make this receptor protein (that is used by HIV to infect cells) on their immune system, therefore HIV doesn’t affect them
When a mutation is passed on: it becomes a new allele - ANOTHER beneficial mutation: gene to help digestion; allowing for people to become lactose-tolerant, as the body can now break down the lactose from cow’s milk (agricultural society)
- sickle cell anemia CARRIERS
SICKLE CELL ANEMIA
SICKLE CELL ANEMIA: base substitution mutation
Mutation is found in the gene that codes for haemoglobin in red blood cells
Mutation causes shape in haemoglobin, therefore change in shape of the RBC’s, causing them to look like a ‘sickle’
GAG mutated to GTG, VALINE is added to the polypeptide chain instead of GLUTAMIC ACID
symptoms and effect of sickle cell anemia
SYMPTOMS:
Fatigue
Weakness
Shortness of breath
EFFECTS:
Oxygen cannot be carried properly by the mutated RBC
Haemoglobin crystallizes (hardens/stiffens) RBC, making them less flexible; they become stuck in capillaries so blood flow is slowed/blocked
ADVANTAGES:
CARRIERS are immune to malaria, as the parasite dies in the cells with carry the sickle cell anemia gene mutatio
THE HUMAN GENOME PROJECT:
catalog the entire sequence of DNA for a human being (started MAY 2000)
how does the human genome project catalog dna?
DNA Fragmentation, primer sequence is added to start process
DNA polymerase attaches to one copy of the first fragment and adds free nucleotides
Strands are separated by size during gel electrophoresis
Gel Electrophoresis
Gel electrophoresis is a way of comparing two or more samples of DNA
Separation of the DNA fragments are based on their size and charge
In a gel electrophoresis lab a mixture of restriction enzymes, DNA samples and loading dye (to indicate where the fragments are and to weigh down the mixture) are inserted into their respective wells in an agarose gel (this mixture is measured with a micropipette which inserts indicated amounts into microcentrifuge tubes, the mixture is then mixed and collected to the bottom of the microcentrifuge tube using a pulse centrifuge).
The electrophoresis chamber is then connected to a power supply and since DNA is slightly negatively charged it begins moving across the gel towards the positive electrode.
USING DNA TO MAKE MEDICINE:
Find beneficial molecules that are produced naturally in healthy people
Find out which gene controls the synthesis of a desirable molecules
Copy that gene and create therapeutic proteins
CHROMOSOMES in PROKARYOTES:
Contain circular strand of DNA and reproduce through binary fission, has only one chromosome, whereas when two parents are involved (like in eukaryotes), there are pairs
CONTAIN plasmids which can be used for genetic engineering
PLASMIDS
PLASMIDS; not connected to main bacterial chromosome, replicate independently, and can travel through different cells, can help the cell adapt (e.g. become immune to antibiotics): GENETIC ENGINEERING
EUKARYOTES CHROMOSOMES
DNA is in the form of chromosomes, which carry the information needed for the cell to exist
When the cell is not dividing, the chromosomes are not visible, as they are in the form of chromatin
