Unit 6 #2 - Genetics Flashcards
what did nettie stevens discover
1. genes are located on the recently discovered CHROMOSOMES inside the cell nucleus. 2. in certain insects, the Y chromosome is only found in males.
Also, pioneered use of fruit fly as model organism
What is the SRY gene
carried by the y chromosome in mammals, causes gonad to develop as a testis (has the coding for the protein responsable to do this). If no SRY gene, then the embryo develops as female, by default.
What genes (3+) are on the y chromosome in humans
- SRY gene
- Gene that gives hairy ears
- other genes responsable for sperm+testis development
WHat is the difference between the X and Y chromosome?
X chromosome nothing to do with sex and it has many genes.
What is the fruit fly life cycle?
embryo, 1st instar larva, 2nd instar larva, 3rd instar larva, prepupa, pupa
What is particular about fruit fly chromosomes
4 pairs (2n=8) and they are giant chromosomes (eat a lot, make a lot of saliva and replicate a lot)
In fruit flies, what reabsorbs the nutrients from the old larval body to become parts of the adult fly?
Homologous imaginal discs
What is the purpose of a chi square and what needs to be looked at to determine if your suspicion is probable or not
Purpose: Quantifying your suspicion and the discrepancy between what you observe and expect
if probability greater than 0.05 = great probability that what you expect will occur/fail to reject null hypothesis
if chi square value calculated is smaller = small discrepancy between between what is observed and expected/fail to reject null hypothesis
When n=2, what is the size of the chromosmes relative to one another
2 sets of chromosomes, 1 big, 1 small
Are traits controlled by one gene
Often traits are controlled by more than one gene
What did mendel solve? (1866)
Darwin’s question about how traits were inherited.
Mendel realised that:
1. each trait is controlled by TWO « factors », one from
the mother and one from the father
2. One factor dominates the other – they do not blend
with each other. (dominate vs recessive)
whereas, darwin thought essence from mother anf father, for example, produced a child…no!
What is chromatin
DNA+protein
what are genes made of
DNA
Provide an example of self-fertilization and another type of pollination
Self-fertilizing (self-pollination): pea flower; produces pollen (male gamete), which is trapped in the flower because it is closed, and ovules (female gamete) so it self-fertilizes
Cross-pollination: remove male organs (so no pollen production) and use brush to collect and fertilizes ovules with the pollen from another plant.
What are pure lines
individuals that always give the same phenotype in the offspring
eg pp always gives white flowers for example (its a true-breeding) or PP
What are sport
Individual that has the phenotype of a great-grandparent or grandparent
Why are genotypes represented with 2 letters eg. PP or Pp…
Because everybody has 2 versions of the gene
what does P, F1, F2 means
Generations: P=parents, F1=child, F2=grandchild….
what is a genotype
allele combination
what is a phenotype
physical manifestation of the allele combination
what is a gene
DNA code for a particular trait
What is locus
Position of gene on a chromosome
eg. “here (pointing part of chromosome) is the locus for flower-color gene”
what is an allele
alternative version a a gene
Do males and females contribute equally to the appearance of the offspring
Yes, doesnt matter if the genetic determinant ie round seeds comes from male or female. Mendel showed this by reciprocal crosses: round seed male to wrinkled seed female and obtained same phenotypes in offspring for round seed female to wrinkle-seed male
How did mendel use the scientific method?
- Selected EITHER: OR traits eg. for garden peas: flower color, seed color, seed texture, pod color…
- Used plants that were self-fertilising
- Controlled variables
- Reciprocal crosses
- Independent variable: the parents
- Dependent variable: offspring
- Quantified results and analysed them mathematically
Name dominate and recessive traits in humans with their phenotypes
eg: recessive
Albinism: lack of melanin pigmentation
cystic fibrosis: abnormal gland secretion leading to liver degenerations and lung failure
Alkaptonuria: inability to metabolize homogentisic acid (urine black when exposed to light)
Hemophilia: inability blood clots properly
Sickle cell anemia: defective hemoglobin that causes red blood cells to curve and stick togheter
eg dominant traits: (also genetic diseases caused by dominant traits)
Huntington disease: degenerations of nervous system starting in middle age
Hypercholesterolemia: elevated levels of blood cholesterol and risk of heart attack
Polydactyly: extra fingers and toes
What do genes cause to be made?
Enzymes (chemicals that bring 2 substances together to make a chemical reaction that gives us our appearance) eg gaited horses trot this way because of DMRT3 gene that controls an enzyme that effects nervous system
What is Mendel’s first law
The Principle of Segregation:
The two alleles for a gene segregate during
gamete formation and are rejoined at random,
one from each parent, during fertilizations. So, gametes have one allele for seed shape since the alleles segregated/”separated” during meiosis I.
How can you tell that a plant is true-breeding?
Do a test cross with a homozygote recessive, if true-breeding will all give the same phenotype
What often causes hereditary diseases
Recessive alleles, and more particularly when homozygote recessive. They are versions of genes that stop gene functioning because they mutated. They make no gene product.
What does inbreeding cause? eg. pedigree animals
increases the likelihood that the offspring will inherit two copies of a recessive allele
Name harmless recessive alleles
Tongue rolling T Widow’s peak W Unattached earlobes E Hitchiker’s thumb h Lex thumb on top when clapping L Mid-digit hair M
Can genetic disease be cause by dominant genes and not only recessive genes?
Yes, usually because they are overly expressed
eg.
Huntington disease : degenerations of nervous system starting in middle age
Hypercholesterolemia: elevated levels of blood cholesterol and risk of heart attack
Polydactyly: extra fingers and toes
Hereditary sensory and autonomic neuropathy HSAN: dont feel pain
What is Mendel’s hypothesis on flower colors for garden peas
Each parent contributes a factor of inheritance. The combination of these two factors determine the flower colour.
What is mendels second law
The Principle of Independent Assortment
In a dihybrid cross, the alleles of each gene assort
independently
*Dihybrid cross: AaBb x AaBb
