Unit 6 #2 - Genetics

Question 1

what did nettie stevens discover

Answer 1

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

Question 2

What is the SRY gene

Answer 2

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.

Question 3

What genes (3+) are on the y chromosome in humans

Answer 3

1. SRY gene
2. Gene that gives hairy ears
3. other genes responsable for sperm+testis development

Question 4

WHat is the difference between the X and Y chromosome?

Answer 4

X chromosome nothing to do with sex and it has many genes.

Question 5

What is the fruit fly life cycle?

Answer 5

embryo, 1st instar larva, 2nd instar larva, 3rd instar larva, prepupa, pupa

Question 6

What is particular about fruit fly chromosomes

Answer 6

4 pairs (2n=8) and they are giant chromosomes (eat a lot, make a lot of saliva and replicate a lot)

Question 7

In fruit flies, what reabsorbs the nutrients from the old larval body to become parts of the adult fly?

Answer 7

Homologous imaginal discs

Question 8

What is the purpose of a chi square and what needs to be looked at to determine if your suspicion is probable or not

Answer 8

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

Question 9

When n=2, what is the size of the chromosmes relative to one another

Answer 9

2 sets of chromosomes, 1 big, 1 small

Question 10

Are traits controlled by one gene

Answer 10

Often traits are controlled by more than one gene

Question 11

What did mendel solve? (1866)

Answer 11

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!

Question 12

What is chromatin

Answer 12

DNA+protein

Question 13

what are genes made of

Answer 13

DNA

Question 14

Provide an example of self-fertilization and another type of pollination

Answer 14

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.

Question 15

What are pure lines

Answer 15

individuals that always give the same phenotype in the offspring

eg pp always gives white flowers for example (its a true-breeding) or PP

Question 16

What are sport

Answer 16

Individual that has the phenotype of a great-grandparent or grandparent

Question 17

Why are genotypes represented with 2 letters eg. PP or Pp…

Answer 17

Because everybody has 2 versions of the gene

Question 18

what does P, F1, F2 means

Answer 18

Generations: P=parents, F1=child, F2=grandchild….

Question 19

what is a genotype

Answer 19

allele combination

Question 20

what is a phenotype

Answer 20

physical manifestation of the allele combination

Question 21

what is a gene

Answer 21

DNA code for a particular trait

Question 22

What is locus

Answer 22

Position of gene on a chromosome

eg. “here (pointing part of chromosome) is the locus for flower-color gene”

Question 23

what is an allele

Answer 23

alternative version a a gene

Question 24

Do males and females contribute equally to the appearance of the offspring

Answer 24

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

Question 25

How did mendel use the scientific method?

Answer 25

1. Selected EITHER: OR traits eg. for garden peas: flower color, seed color, seed texture, pod color... 2. Used plants that were self-fertilising 3. Controlled variables 4. Reciprocal crosses 5. Independent variable: the parents 6. Dependent variable: offspring 7. Quantified results and analysed them mathematically

Question 26

Name dominate and recessive traits in humans with their phenotypes

Answer 26

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

Question 27

What do genes cause to be made?

Answer 27

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

Question 28

What is Mendel's first law

Answer 28

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.

Question 29

How can you tell that a plant is true-breeding?

Answer 29

Do a test cross with a homozygote recessive, if true-breeding will all give the same phenotype

Question 30

What often causes hereditary diseases

Answer 30

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.

Question 31

What does inbreeding cause? eg. pedigree animals

Answer 31

increases the likelihood that the offspring will inherit two copies of a recessive allele

Question 32

Name harmless recessive alleles

Answer 32

``` 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 ```

Question 33

Can genetic disease be cause by dominant genes and not only recessive genes?

Answer 33

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

Question 34

What is Mendel's hypothesis on flower colors for garden peas

Answer 34

Each parent contributes a factor of inheritance. The combination of these two factors determine the flower colour.

Question 35

What is mendels second law

Answer 35

The Principle of Independent Assortment In a dihybrid cross, the alleles of each gene assort independently *Dihybrid cross: AaBb x AaBb