Lec 4. Basic principles of Heredity

Question 1

Who is Mendel?

Answer 1

Set out mathematically description how some genes are passed down from one generation to the next.

Question 2

What was the model organism Mendel used?

Answer 2

Pea plant

Question 3

What does homozygous mean?

Answer 3

True breeding. The alleles are identical

Question 4

Define a Monohybrid cross

Answer 4

Cross between two parents that differ in a single characteristic

Question 5

What four conclusion can be made from the Monohybrid cross?

Answer 5

Each characteristic is encoded by two genetic factors, these two characteristics somehow separate during reproduction, the concept of dominant and recessive traits, two alleles separate with equal probability into the gametes.

Question 6

What is Mendel’s first law?

Answer 6

Principle of segregation

Question 7

Define principle of segregation

Answer 7

For every characteristic we have a pair of genes and they segregate INDEPENDENT from on another and only one is passed from each parent.

Question 8

What is independent assortment?

Answer 8

Alleles segregate independently when gametes are formed.

Question 9

Define the concept of dominance

Answer 9

When two different alleles are present in a genotype, only the trait encoded by one of them-the dominant allele- is observed in the phenotype. The other is called recessive.

Question 10

How do monohybrid crosses explain the principle of segregation?

Answer 10

Capital=dominant. Lower case= recessive trait. The symbols in the crosses correspond to alleles on chromosomes.

Question 11

What is the Chromosomal Theory of Heredity (1902)?

Answer 11

identified chromosomes as the genetic material responsible for Mendelian inheritance. (sutton)

Question 12

How is cystic fibrosis caused?

Answer 12

Mutations in the CFTR gene. Mutations are usually recessive

Question 13

Define probablility

Answer 13

likelihood of the occurrence of an event

Question 14

What is probability used for in genetics?

Answer 14

predict the outcome of a genetic cross

Question 15

How is probability quantified as a number?

Answer 15

Between 0 and 1. 0 is impossible. 1 is certain.

Question 16

What are probabilities numerically described as?

Answer 16

As the number of desired outcomes divided by the total number of all outcomes

Question 17

What is the multiplication rule?

Answer 17

Multiply the probability of independent events happening simultaneously.

Question 18

What is the addition rule?

Answer 18

When two events are mutually exclusive, the probability that either A OR B will occur is the sum of the probability of each event. Big word here is OR.

Question 19

What is conditional probability?

Answer 19

probability of an event A, given that another B has already occurred.

Question 20

What is the binomial equation used for?

Answer 20

Used to calc simple and complicated crosses with multiple genes

Question 21

What is the binomial equation?

Answer 21

(p+q)^n

Question 22

What do the variables in the binomial equation stand for?

Answer 22

p= frequency of one outcome. q= frequency of the other outcome. n= number of events. Know that p+q equal 1.

Question 23

What is a Dihybrid Cross?

Answer 23

a cross that deals with 2 traits, with differing alleles.

Question 24

How did Mendel reveal the principle of independent assortment?

Answer 24

By examining the behavior two traits simultaneously. Dihybrid cross.

Question 25

Where does the principle of independent assortment result from?

Answer 25

From the independent separation of chromosomes in Anaphase I of meiosis.

Question 26

What is a branch diagram and what can it be used to determine?

Answer 26

Another way to show a punit square, determines the phenotypes and expected proportions of offspring from a dihybrid cross.

Question 27

What do Dihybrid crosses show?

Answer 27

Relate the principle of independent assortment to meiosis. Genes located on different chromosomes will sort independently.

Question 28

Define Chi-square Goodness of Fit

Answer 28

A statistical test that indicated the probability that the difference between the observed and expected values is due to chance

Question 29

What are some assumptions of a chi-square goodness of fit?

Answer 29

Random sample, sample size, independence

Question 30

Define random sample

Answer 30

the sample data is a random sample of a larger population

Question 31

Define sample size

Answer 31

is sufficiently large to prevent small sample error

Question 32

Define independence

Answer 32

observations are independent of each other

Question 33

Define degrees of freedom

Answer 33

total number of things that could of happened minus 1

Question 34

What chi square value indicates significance?

Answer 34

below .5

Question 35

What does a chi square value of .5 or below indicate?

Answer 35

What was observed was not due to chance

Question 36

Short answer question. How are the principle of segregation and independent assortment related and how do they differ?

Answer 36

Genes encoding different characteristics separate and assort INDEPENDENTLY of one another when they are not located close together on the same chromosome. During this process, 2 alleles of the same gene encoding one characteristic still have to be segregated from each other during the formation of gametes.

Question 37

What is the problem with multiple testing?

Answer 37

Multiple simultaneous statistical tests increase the chance of finding a false positive since so many variables were tested.

Question 38

How do we deal with the problem with multiple testing?

Answer 38

Multiple testing correction

Question 39

Define multiple testing correction

Answer 39

re-calculating probabilities from the multi repeated test. We make the threshold to achieve significance harder to achieve to avoid false positives.