Genetics- Chapter 5 and 6

Question 1

Gregor Mendel

Answer 1

• “father of inheritance”

studied inheritance in pea plants

Question 2

Why did Mendel study Pea Plants?

Answer 2

• they produce quickly and in large numbers
• matured quickly
• showed many traits with only 2 variations (e.g. tall or short, yellow or green)

Question 3

Gene

Answer 3

• Sections of DNA that have instructions for a specific trait
• Comes in alternate forms called alleles

Question 4

Alleles may be…

Answer 4

Dominant or Recessive

Question 5

Define dominant and state what letter it is represented as

Answer 5

Dominant- codes for a trait that is ALWAYS expressed “shows up”
- represented as an uppercase letter

Question 6

Define Recessive and state what letter it is represented as

Answer 6

codes for a trait that is usually hidden “masked by a dominant gene”
- represented by a lower case letter

Question 7

True Breeding

Answer 7

only making an offspring of their kind either by self fertilization or crossing with another of their kind

Question 8

Cross

Answer 8

mating between 2 individuals

Question 9

Monohybrid Cross

Answer 9

a cross designed to study the inheritance of only one trait

Question 10

P Gen

Answer 10

The parent plants used in a cross

Question 11

First Final or F1 Gen

Answer 11

the offsprings of the P Gen cross

Question 12

Law of Dominance

Answer 12

When individuals with offspring traits were crossed, the offspring will always express the dominant trait

Question 13

F2 Gen

Answer 13

Offsprings of the F1 cross

Question 14

Law of Segregation

Answer 14

1) organisms inherit two copies of genes, one from each parent
2) organisms donate only one copy of each gene to their gametes because the genes separate during gamete formation to give offspring 1 allele

Question 15

Phenotype

Answer 15

“physical”; describes how genes are expressed (aka what shows up
e.g. tall or short

Question 16

Genotype

Answer 16

“gene”; describes genetic makeup

e. g. AA, Aa, aa
* may be heterozygous or homozygous

Question 17

Homozygous

Answer 17

2 of the SAME copies of a gene

e.g. AA or aa

Question 18

Heterozygous

Answer 18

2 DIFFERENT copies of a gene

e.g. Aa

Question 19

Test Crosses

Answer 19

crossing an individual with an unknown genotype with a homozygous recessive individual
- phenotypes of the resulting offspring may indicate the genotype of the unknown

Question 20

Pedigrees

Answer 20

illustrates the inheritance of a trait among a group of related individuals
- useful when following a harmful trait, or dog breeding

Question 21

Pedigree Symbols

Answer 21

square- male
circle- female
shaped square and circle- have traits
straight line joining 2 symbols- mating or married
horizontal line- line of descent
straight line that drops to 2 shapes- siblings or offsprings

Question 22

Incomplete Dominance

Answer 22

neither allele dominates the other instead both influence each other; results in partial expression of both traits
e.g. red + white = red, white and pink

Question 23

Codominance

Answer 23

Both alleles for a trait are equally dominant. results in a phenotype that shows both homozygous phenotypes
e.g. red hair cows (RR) + white hair cows (WW) = Roan (RW); cows with both red and white hairs

Question 24

Blood types and their pheno and geno types

Answer 24

Phenotype:       Genotype:
       A                   AA or AO
       B                   BB or BO 
      AB                  AB
       O                   OO

Question 25

Complete Dominance

Answer 25

Complete dominance over the recessive allele

e.g. Rr

Question 26

Key info on Sex- Linked Inheritance

Answer 26

Males only have 1 X chromosome and their Y isnt homologous. therefore men can only have 1 X chromosome ( this is called Hemizygous)

Question 27

Sex- Linked Inheritance

Answer 27

describes an allele that is found on one of the sex chromosomes either X or Y that is expressed when passed onto teh offspring

Question 28

Barr Body

Answer 28

a single inactive X chromosome

Question 29

Multitrait Inheritance

Answer 29

the affect one inheritance trait can have when crossed with another
e.g. crossing round (R) and yellow (Y) seeded plants with a wrinkled (r) and green (y) seeded plant

Question 30

Law of Independent Assortment

Answer 30

The inheritance of one trait does not affect the inheritance of another
- except if genes are linked

Question 31

Product Law

Answer 31

the probability of 2 or more events occurring together is the product (multiply) of their individual probabilities
e.g. RrYy x RrYy = Rr x Rr and Yy x Yy

Question 32

2 types of Variation

Answer 32

Discontinuous Variation- trait is determined by activity of one gene and produces “clear cut” phenotypes
e.g. tall or short

Continuous Variation- Trait is determined by activity of multiple genes (polygenic) and produces a range of phenotypes
e.g. human height and skin colour

Question 33

List the 5 people and or groups and what they discovered about DNA

Answer 33

1. Meisher- isolate the substance found in the nucleus, called it the nuclein
2. Hershey and Chase- confirmed that DNA contained heredity information not proteins
3. Levene- discovered chemical composition of DNA, made of a building block called a Nucleotide, which has 3 parts:
   - a sugar
   - a negatively charged phosphate group
   - 1 of 4 nitrogen bases; Adenine, Guanine, Cytosine and Ihymine
4. Chargaff- found that the amounts of A and T were always equal in a sample of DNA and so were C and G
5. Watson and Crick- determined that DNA exists as a double helix “twisted ladder”

Question 34

DNA Structure

Answer 34

• always has a complementary base; A with T and C with G

- ladder analogy; sides made of alternating squares and phosphates, steps were made of nitrogen base pairs

Question 35

Mutation

Answer 35

change in the sequence (order) of nitrogen bases in the DNA
- this can happen in interphase during DNA replication
- semi conservative; each new molecule of DNA has half of the original molecule
can be spontaneous: occur without specific cause
can be induced: caused by exposure to hazardous chemicals, radiation, and viruses
- only heritable if it occurs in the production of gametes

Question 36

Result of a mutation can be….

Answer 36

positive- helpful to an individual (ie lactose intolerant)
negative- harms the individual (ie genetic disease where we cant make protein to to fight it off)
neutral- has no impact (ie change doesnt affect protein or it occurs in areas of DNA without genes

Question 37

First type of Mutation

Answer 37

Point Mutation: small change in DNA, several or few bases are changed

• Base Pair substitution: one bp is switched with another
• Frameshift Mutation: a base pair is added or deleted

Question 38

second type of mutation

Answer 38

Chromosomal Mutation: large change in DNA, affects 100s or 1000s of bp
- inversion: chunk of chromosome is removed and reinserted backwards
-translocation: extra chunk of chromosome is attached to another chromosome
deletion:chunk of chromosome is lost
duplication- chunk of chromosome is repeated

Question 39

Human Genotype Project

Answer 39

began in 1990, with goal to identify the sequence (order) of the entire 3 billion nitrogen base pairs in human DNA

Question 40

Non-Coding DNA

Answer 40

• About 2%

- contains actual genes that can be used to make proteins

Question 41

Coding DNA

Answer 41

• About 98%

- does not contain genes, some is functional (regulates gene activity) and some is non-functional