Topic 11: Mendelian Genetics

Question 1

Who discovered the basic principles of heredity by breeding garden peas?

Answer 1

Gregor Mendel in 1867

Question 2

When did we know genes were encode by DNA?

Answer 2

1944 Griffith

Question 3

Who came up with DNA structure?

Answer 3

1953 James Watson and Francis Crick

Question 4

What is hybridization?

Answer 4

cross breeding

Question 5

What are the results of Mendel’s experiments came the two fundamental principles of genetics?

Answer 5

1. Law of Segregation
2. Law of Independent Assortment 2

Question 6

What is Mendel’s first conclusion?

Question 7

What is Mendel’s first conclusion?

Answer 7

1. They are alternative versions of ‘heritable units’ that can be passed on to progeny
   -these are called alleles
   -arise from mutations of the DNA sequence of a gene
   -alters or eliminates the function of the encoded protein

Question 8

What is Mendel’s second conclusion?

Answer 8

2. For each character, an organism receives two copies (i.e two alleles) of any given gene, one from each parents

Question 9

What is Mendel’s third conclusion?

Answer 9

If alleles differ at a locus, then one must be dominant
-dominant vs. recessive

Question 10

What is Mendel’s fourth conclusion?

Answer 10

4. The Law of Segregation: the two alleles for a heritable character segregate (separate from each other) during gamete formation and end up in different gametes

a.) start with set of homologous chromosomes
b.) duplicate their DNA
c.) anaphase I separates the homologous chromosomes
d.) anaphase II separate the sister chromatids
e.) half the gametes get one allele of a gene, the other half gets the other

Question 11

What is the phenotype?

Answer 11

the observed trait of a characteristic

Question 12

What is the Genotype?

Answer 12

the genetic makeup that produces the phenotype

Question 13

What is a homozygote or homozygous ?

Answer 13

organism has a pair of identical alleles for a gene

ex. PP or pp

Question 14

What is a heterozygote or heterozygous?

Answer 14

if an organism has a pair of alleles for a gene that are different

ex. Pp and pP

Question 15

What is a monohybrid cross? Dihybrid cross?

Answer 15

MONO: follows only one character
DI: follows two characters at once

Question 16

What is the Law of Independent Assortment?

Answer 16

states that two or more genes will assort independently into gametes
-each pair of alleles segregates independently of any other pair of alleles during gamete formation

Question 17

What was Mendel’s observed phenotypic ratio?

Answer 17

9:3:3:1

Question 18

What happens if genes are realllllllly close on a chromosome?

Answer 18

they are linked
-alleles of these genes will be packaged into chromosomes together during meiosis

Question 19

What happens if genes are reallllllly far apart on the same chromosome?

Answer 19

the odds of crossing over between them is very likely
-this makes it so that they’re no longer linked and the alleles can assort independently

Question 20

What is pleiotropy?

Answer 20

occurs when one gene (or the alleles of one gene) affect multiple phenotypes

Question 21

What is Co-dominance ?

Answer 21

results in the heterozygous having a unique phenotype that is different from the homozygous phenotypes

ex. albinism causes lack of melanin in skin, eyes, hair but can also cause light sensitivity and strabismus in eyes

Question 22

What is Penetrance?

Answer 22

if a homozygous genotype doesn’t always produce a specific phenotype in all members of the group