Chapter Two: Genetics & Inheritance

Question 1

What did Gregor Mendel’s work conclude? (5)

Answer 1

1. Each parent contributes one factor of each trait shown in offspring (alleles)
2. The two alleles contribute equally to offspring traits
3. The blending theory was discounted
4. Males & females contribute equally to offspring traits
5. Acquired traits are not inherited.

Question 2

What made Mendel’s work unique? (3)

Answer 2

1. Methodical approach to a definite problem
2. Use of clear-cut variables
3. Application of statistics to a biological problem

Question 3

Law of Dominance

Answer 3

One of the factors for a pair of inherited traits will be dominant and the other recessive, unless both factors are recessive

Question 4

Law of Segregation

Answer 4

Paired alleles separate during gamete formation with each gamete receiving either one trait or the other

Question 5

Law of Independent Assortment

Answer 5

When gametes are formed, alleles assort independantly

Question 6

Genotype

Answer 6

Specific genetic makeup; written in terms of alleles.

Question 7

Trait

Answer 7

Inheritable characteristic

Question 8

Monohybrid cross

Answer 8

Cross examining ONE trait

Question 9

Dihybrid Cross

Answer 9

Cross examining TWO traits

Question 10

Test Cross

Answer 10

Cross used to determine if a parent is homozygous or heterozygous for a dominant trait. The parent is crossed with a heterozygous recessive individual

Question 11

Product Rule of Probability

Answer 11

The chances of a gamete having multiple traits is the product of their individual chances.

Question 12

Codominance

Answer 12

Two equally dominant alleles are expressed independantly

Question 13

Polygenetic Inheritance/Multiple Allele Inheritance

Answer 13

More than one gene is responsible for a trait, results in continuous variation within the population.

Question 14

Lethal Alleles

Answer 14

Allele that causes death to an individual during embryonic development.

Dominant & Recessive

Question 15

Probability

Answer 15

The chance of an event occurring.

Question 16

Theoretical Probability Formula

Answer 16

Probability = # of likely outcomes/total # of outcomes

Question 17

Rules of Probability (3)

Answer 17

1. The actual outcome will have a ratio closer to the predicted probability as # of trials increase
2. Past outcomes don’t affect future outcomes
3. The chance that two or more independent events will occur at the same time is equal to the product of their individual chances

Question 18

Why are males more likely to get sex-linked traits than females?

Answer 18

Males only have one X-chromosome, so the allele is always expressed. Females, having two X-chromosomes, appeal to the rule of dominance.

Question 19

Pedigree

Answer 19

Tool designed to show inherited phenotypes and can be used to logically deduce genotypes as well.

Question 20

Autosomal Dominant disease

Answer 20

Disease is passed from father to son (not sex-linked)

Males and Females affected with roughly the same probability

Question 21

Autosomal Recessive Disease

Answer 21

Males and females equally likely to be affected.

The recurrence risk to the unborn sibling is 25%

Question 22

Non-Disjunction

Answer 22

An accident of Mitosis or Meiosis where a tetrad (Meiosis) or a pair of sister chromatids (Mitosis) fail to separate properly.

Question 23

Deletion

Answer 23

A chromosomal fragment is lost.

Question 24

Duplication

Answer 24

A chromosome fragment reattaches to its homologous chromosome, creating a duplicate sequence.

Question 25

Inversion

Answer 25

A chromosomal fragment reattaches it is’s original chromosome in the reverse sequence.

Question 26

Translocation (2)

Answer 26

1. Insertions: a chromosomal fragment is attached to a non-homologous chromosome
2. Exchanges: homologous chromosome pairs exchange chromosomal fragments

Question 27

Karyotype

Answer 27

Collection of photographs of chromosomes during mitosis, arranged in homologous pairs snd placed in order of descending size.

Question 28

Aneuploidy

Answer 28

An abnormal chromosome number:
Trisomy (+1)
Monosomy (-1)

Question 29

Incomplete Dominance

Answer 29

The dominant trait does not completely mask the recessive trait.