Unit 3 (Mendelian Genetics)

Question 1

What are Mendelian Genetics?

Answer 1

The study of patterns of inheritance.

Question 1

Who is the father of genetics? When did he live?

Answer 1

1. Gregor Mendel
2. (1822-1884)

Question 2

What is Gregor Mendel known for? Why is he so impressive?

Answer 2

1. He discovered the basic patterns of inheritance by studying pea plants.
2. He did this without any knowledge of DNA, chromosomes, or genes.

Question 3

What were the studied traits of Mendel’s pea plants?

Answer 3

The flowers were either red/white.
The pea seeds were either round/wrinkled.

Question 4

Explain Mendel’s First Experiment.

Answer 4

He began by true breeding and then bred the offspring with each other for the following generation.
(P) RR x ww= Rw, Rw, Rw, Rw
(F1) Rw x Rw=RR, Rw, Rw, ww
(F2) RR, Rw, Rw, ww (he didn’t bred these)

Question 5

What were the two statements Mendel concluded from his first experiment?

Answer 5

1. Organisms contain two hereditary factors (genes) for each character (phenotype).
2. Each gamete contains 1 of the 2 genes. Known as the “particulate nature of inheritance”
   (two genes for each trait, one gene from each parent)

Question 6

What is a locus?

Answer 6

The specific place on a chromosome where a gene is located. (The location of a gene on a chromosome)

Question 7

What is a genotype?

Answer 7

The combination of alleles that make up the genetic code. (ex. RR)

Question 8

What is a phenotype?

Answer 8

An observable characteristic (green vs. blue eyes are the same genotype but different phenotype)

Question 9

What is an allele?

Answer 9

A “version” of a gene.

Question 10

What is Incomplete Dominance?

Answer 10

This is when neither allele is dominant. (like a halfway point)

Question 11

What does “true breeding” refer to?

Answer 11

This refers to when one crosses two individuals with homozygous genes.

Question 12

What does “hereditary factors” refer to?

Answer 12

This is how Mendel referred to what we now call, “genes.”

Question 13

What does Mendel’s theory of the “particulate nature of inheritance” refer to?

Answer 13

Mendel’s theory of how traits are passed from parent to child. This theory contradicted the current “blending” theory of the time.
- Particles (genes) are passed on from parent to child. They can be carried even if they are not visible.
(ex. he made two red plants have a white child, this contradicts the blending theory)

Question 14

What does it mean for a genotype to be homozygous? What are two ways a gene can be homozygous?
What does it mean for a genotype to be heterozygous?

Answer 14

1. It means the genotype is comprised to two of the same alleles.
   (RR, rr) This is the same allele on both chromosomes of a homologous pair.
2. It means the genotype is comprised of two different alleles. (Rr)

Question 15

What is a Monohybrid Cross?

Answer 15

Fertilization between two true-breeding parents that differ in only one characteristic is called a monohybrid cross.

Question 16

What is cystic fibrosis? What are the three possible genotypes regarding cystic fibrosis?

Answer 16

1. Cystic fibrosis is a recessive genetic disorder that is quite lethal.
2. He explained that there are three genotype options.
   -You are healthy and not a carrier. (RR)
   -You are healthy and a carrier. (Rr)
   -You have cystic fibrosis (rr)

Question 17

What are the alleles of the parent generation that leads to a dihybrid cross? What is a Dihybrid Cross?

Answer 17

1. Parent Gen.= A homozygous dominant and homozygous recessive parent (YYRR x yyrr)
2. A dihybrid cross is the F1 generation, the crossing of two heterozygous (YyRr x YyRr) organisms.

Question 18

What is the difference between a Dihybrid and a Monohybrid Cross?

Answer 18

These are both the crossing of parents in the F1 generation. HOWEVER, a monohybrid cross is the crossing of one trait, and dihybrid is the crossing of two traits.

Question 19

What are the four possible gametes Rr x Yy can make?

Answer 19

(RY) (Ry) (rY) (ry)

Question 20

What is the numerical pattern dihybrid crosses follow genotype wise?

Answer 20

9 (shows both dominant traits)
3 (shows one of both)
3 (shows one of both)
1 (shows both recessive traits)

Question 21

What did Mendel conclude after conducting his dihybrid cross experiment on the pea plants?

Answer 21

The gametes occur in equal proportion and the different traits pass to the gametes independently. (slide 25-26🧡)

Question 22

What is Independent Assortment?

Answer 22

The rule that genes for different traits are inherited independently of each other.

Question 23

What is the difference between linked and unlinked loci?

Answer 23

Linked Loci= on the same chromosome
Unlinked Loci= on seperate chromosomes

Question 24

What is an X-Linked trait? How is an x-linked trait expressed?

Answer 24

1. An x-linked trait is a trait that only has genes on the X-chromosome.
2. In order for this trait to be expressed the man must get the trait from his mother. (Y from the father, X from the mother)

Question 25

What are Autosomes?

Answer 25

Any chromosome that isn’t a sex chromosome.
(a sex chromosome is called a gamete, all others are called autosomes)

Question 26

Some x-linked traits are recessive. How does this affect their expression in men?

Answer 26

If a man gets a x-linked trait, even if it’s recessive, it’ll express itself. This is because a man doesn’t have another allele to mask the trait. (only one X chromosome)

Question 27

What are the sex-chromsomes in women and men?

Answer 27

Women (XX)
Men (XY)

Question 28

What is a “Barr Body?”

Answer 28

The unexpressed chromosome in a women

Question 29

What is Polygenic Inheritance? Give an example.

Answer 29

This is when one character is determined by more than once locus. (hair can be many possible colors) (🧡 locus, not gene?)

Question 30

What is Multifactorial Inheritance?

Answer 30

This is when a trait is determined both by genetic and environmental factors. (ex. weight)

Question 31

What are the two most common forms of inheritance in organisms?

Answer 31

1. Polygenic Inheritance
2. Multifactorial Inheritance

Question 32

What is Pleiotropy?

Answer 32

This is when once locus affects more than one character in an organism.