Mendelian Genetics and Probabilities (Lecture 4)

Question 1

Mendel’s peas were highly inbred, what does this mean?

Answer 1

They are, therefore “bred true or true-breeding or pure bred”
e.g. when two tall plants were crossed, they only produced tall progeny

Question 2

What does the flower structure of the pea plant promote?

Answer 2

The flower structure promoted self-fertilization

Question 3

Mendel’s experiments were designed so that he could study what?

Answer 3

One trait at a time

Question 4

What is a gene?

Answer 4

An inherited factor (encoded in the DNA) that helps determine a characteristic

Question 5

What is an allele?

Answer 5

One of two or more alternative forms of a gene

Question 6

What is a locus?

Answer 6

A specific place on a chromosome occupied by an allele

Question 7

What is a genotype?

Answer 7

Set of alleles possessed by an individual organism

Question 8

What does it mean to be heterozygote?

Answer 8

An individual organism possessing two different alleles at a locus

Question 9

What does it mean to be homozygote?

Answer 9

An individual organism possessing two of the same alleles at a locus

Question 10

What is a phenotype or a trait?The appearance or manifestation of a characteristic

Answer 10

The appearance or manifestation of a characteristic

Question 11

What is a characteristic or character?

Answer 11

An attribute or feature possessed by an organism

Question 12

In alleles, what does an upper case letter refer to?

Answer 12

Refers to the dominant (expressed factor) allele

Question 13

In alleles, what does a lower case letter refer to?

Answer 13

Refers to the recessive (latent factor) allele.

Question 14

Alleles can be designated after the recessive trait, give an example of this.

Answer 14

example: a fly with a genetic mutation causes a white eye, whereas the wild type eye is red. The alleles would be w=white eye; W=red eye.

Question 15

In some cases the alleles are designated after the dominant phenotype, give an example of this.

Answer 15

For example, the allele R for round seeds; r for wrinkled seeds.

RR or Rr for round seeds; rr for wrinkled seeds

Question 16

The allelic combination is called what?

Answer 16

The genotype

Question 17

The physical appearance is called what?

Answer 17

The phenotype

Question 18

Genes exist in different versions called alleles. What do the different alleles code for?

Answer 18

One allele encodes round seeds

A different allele encodes for wrinkled seeds

Question 19

Different alleles for a particular gene occupy the same…

Answer 19

Different alleles for a particular gene occupy the same locus on homologous chromosomes

Question 20

Mendel started with purebred lines. What were these two purebreds and what was their phenotype?

Answer 20

One was purebred for the round seed; the other was purebred for the wrinkled seed. So they were each homozygous for the different alleles!

Question 21

(1 & 2) How did Mendel cross varieties of peas?

Answer 21

To cross different varieties of peas, Mendel removed the anthers from flowers to prevent self-fertilization and dusted the stigma with pollen from a different plant

Question 22

(3 & 4) What did the pollen fertilize, and what did it develop into?

Answer 22

The pollen fertilized ova, which developed into seeds. The seeds grew into plants.

Question 23

(5) What is P and what happened at this stage?

Answer 23

P is the parental generation. At this stage Mendel crossed two homozygous varieties of peas.

Homozygous round seeds x Homogyzous wrinkled seeds

Question 24

(6) What is F1 and what happens at this stage?

Answer 24

F1 is the First Filial Generation. All the F1 seeds were round. Mendel allowed plants grown from these seeds to self-fertilize

Question 25

(7) What is F2 and what happens at this stage?

Answer 25

F2 is the Second Filial Generation. This is the result of self-fertilization. 3/4 of F2 seeds were round and 1/4 were wrinkled a 3:1 ratio.

Question 26

What is the conclusion of the traits of the parent plants?

Answer 26

The traits of the parent plants do not blend. Although F1 plants display the phenotype of one parent, both traits are passed to F2 progeny in a 3:1 ratio.

Question 27

After the F2 generation, the fraction of progeny seeds is 3/4 round and 1/4 wrinkled. Provide information for: * Phenotype or Trait * Characteristic * Dominant Phenotype * Recessive Phenotype * Allele Designation * Dominant Genotype * Recessive Genotype * Homozygote * Heterozygote

Answer 27

* Phenotype or Trait: seed texture * Characteristic: round or wrinkled * Dominant Phenotype: Round * Recessive Phenotype: Wrinkled * Allele Designation: R for round; r for wrinkled * Dominant Genotype: RR or Rr * Recessive Genotype: rr * Homozygote: RR or rr * Heterozygote: Rr

Question 28

One of the haploid gametes from Anther will be combined with what?

Answer 28

One of these haploid gametes from the Anther will be combined with one of the haploid gametes from the Stigma to produce a diploid seed.

Question 29

(1 & 2) In the parent generation, Mendel crossed a plant homozygous for round seeds (RR) with a plant homozygous for wrinkled seeds (rr). What happens in the gamete formation process in the p generation?

Answer 29

The two alleles in each plant separated when gametes were formed; one allele went into each gamete

Question 30

(3) In the F1 generation after the fertilization of the P gametes, the gametes fused to produce what plants?

Answer 30

Gametes fused to produce heterozygous F1 plants that had round seeds because round is dominant over wrinkles.

Question 31

(4 & 5) Mendel self-fertilized the F1 to produce the F2 which appeared in what ratio of round to wrinkled?

Answer 31

3:1

Question 32

(6 & 7) Mendel also self-fertilized the F2 seeds to produce the F3 seeds. * Homozygous round peas produced plants with only \_\_\_\_\_\_\_ * Heterozygous plants produced round seeds and wrinkled seeds in a \_\_\_\_\_\_\_\_\_\_ * Homozygous wrinkled peas produced plants with only \_\_\_\_\_\_

Answer 32

* Homozygous round peas produced plants with only round peas * Heterozygous plants produced round seeds and wrinkled seeds in a 3:1 ratio * Homozygous wrinkled peas produced plants with only wrinkled peas

Question 33

What is Segregation? (Mendel's first law) Which state of meiosis is each observation?

Answer 33

``` 1. Each individual organism possesses two alleles encoding a trait (Before meiosis) ``` 2. Alleles separate/segregate when gametes are formed (Anaphase I) 3. Alleles separate/segregate in equal proportions (Anaphase I)

Question 34

What is independent assortment? (Mendel's second law) Which state of meiosis is each observation?

Answer 34

Alleles at different loci Anaphase I assortment separate independently. (Anaphase I)

Question 35

Info slide

Answer 35

Question 36

Create a punnet square using the following information:

Answer 36

Question 37

What is the genotypic and phenotypic ratio from the following F1 generation?

Answer 37

Genotypic ratio: 1 Tt : 1 tt Phenotypic ratio 1 tall : 1 short

Question 38

What is the multiplication rule?

Answer 38

If you roll a die, in a large number of sample rolls, on average 1 of 6 times you will obtain a 4, so the probability of obtaining a 4 in any roll is 1/6. If you roll the die again the probability of getting a 4 again is 1/6. So the probability of getting a 4 on the first roll ***_AND_*** the second roll is 1/6x1/6 = 1/36. \*The operative word here is ***_"AND"_*** \*Getting a four on the first ***_AND_*** second roll

Question 39

The rules of probability - the multiplicative rule If the events A and B are independent, the probability (P) that they occur **_TOGETHER_** is what?

Answer 39

If the events A and B are independent, the probability (P) that they occur **_TOGETHER**_ is the _**PRODUCT_** of their individual probabilities of occurrence.

Question 40

What is the addition rule?

Answer 40

If you roll a die, on average, one out of six times you'll get a 3, and one out of six times you'll get a four. That is, the probability of getting either a 3 or 4 is 1/6 + 1/6 = 1/3. \* The operative word here is **_EITHER**_ or _***OR*_** \*At three ***_OR_*** four

Question 41

The rules of probability - the additive rule (using or) ## Footnote If the events A and B are independent and do not overlap, the probability that at least one of them occurs is the sum of their individual probabilities. Recall Mendel’s peas. What genotype gives rise to Round peas? RR = Round Rr = Round rr= Wrinkled What is the probability of a pea being Round?

Answer 41

It is the probability that the genotype is either RR ***_OR_*** Rr. Therefore, the probability of RR is 1⁄4 or 0.25 The probability of being Rr is 1⁄2 or 0.5 1/4 + 1/2 = 3/4 will be round

Question 42

In cats black fur is recessive to brown fur. If you cross a black cat with a heterozygous brown cat, what is the probability that a kitten would be black?

Answer 42