Chapter 14: Mendel and Heredity

who was the father of genetics

gregor mendel

what did mendel discover

basic principles of heredity by studying garden peas

how did mendel believe traits were inherited

as discrete units (genes) rather than blending

what are the 4 reasons why garden peas were good models

1. short generation time

2. large number of offspring

3. mating is controlled

4. easily observable traits

what is the law of segregation

two alleles for a gene separate during gamete formation

each gamete receives only one allele

law of segregation

what kind of cross does the law of segregation explain

monohybrid

what is the law of independent assortment

genes for different traits assort independently during gamete formation

what kind of cross does the law of independent assortment explain

dihybrid cross

heritable feature that varies among individuals

character

a variant for a character

trait

plants produce offspring identical to them

true-breeding

offspring crosses between parents with different traits

hybrid

parental generation

p generation

unit of heredity

gene

different versions of a gene

allele

both/and

multipy

either/or

add

intermediate phenotype

incomplete dominance

both alleles are fully expressed

codominance

more than two alleles exists in a population

multiple alleles

what is an example of multiple alleles

ABO blood type

one gene affects multiple traits

pleiotropy

what is sickle cell an example of

pleiotropy

what is pleiotropy

One gene affects multiple traits.

one gene affects the expression of another

epistasis

what is epistasis

one genes affects the expression of another

what is lab coat color an example of

epistasis

traits that vary along a continum

polygenic inheritance

doesn't skip generations

dominant

skips generations

recessive

affects males more

sex-linked

what did gregor mendel study on

garden peas

what are the 4 reasons garden peas were so good to study on

short generation time

large number of offspring

controlled mating

distinct traits

A heritable feature that varies among individuals (e.g., flower color)

character

A variant of a character (e.g., purple or white)

trait

Plants that produce offspring identical to themselves when self-pollinated

true-breeding

Crossing of two contrasting true-breeding varieties

hybridization

True-breeding parent generation

P generation

Hybrid offspring of P generation

F1 generation

Offspring when F₁ individuals self- or cross-pollinate

F2 generation

Each plant carries two "factors" (alleles) for each trait that segregate during gamete formation

law of segregation

what happened when Mendel crossed the P generation

all purple plants

what was the P generation cross

purple by white pea plants

what was the conclusion in the F2 population

3 purple; 1 white plant

Alternate versions of genes that account for variations in a character

allele

where is an allele found

specific locus on a chromosome

DNA does code for pigment enzyme

purple flower allele

DNA codes for inactive enzyme

white flower allele

masked in heterozygotes

recessive allele

Two alleles for a heritable trait separate during gamete formation

law of segregation

how many alleles does a gamete get

one

what restores pair of traits

fertilization

Segregation of alleles corresponds to the separation of ______

homologous chromosomes

Tool used to predict offspring genotypes and phenotypes

punnett square

Used to determine if an organism with a dominant phenotype is homozygous (PP) or heterozygous (Pp)

test cross

1 trait

monohybrid cross

what kind of cross results in 3:1 ratio

monohybrid cross

2 traits

dihybrid cross

what kind of cross results in 9:3:3:1 ratio

dihybrid cross

Alleles for different genes segregate independently during gamete formation

law of independent assortment

Applies to genes on different chromosomes or far apart on the same on

law of independent assortment

Explains new combinations of traits not seen in parents

law of independent assortment

Heterozygote shows intermediate phenotype

incomplete dominance

Red × White → Pink.

incomplete dominance

Both alleles are fully expressed

codominance

Human ABO blood types

codominance

IAIA or IAi

type a

IBIB or IBi

type b

IAIB

type AB

ii

type o

Genes have more than two alleles in a population

multiple alleles

One gene influences multiple traits

pleiotropy

Sickle-cell anemia affects blood shape, oxygen transport, and disease resistance.

pleiotropy

One gene affects the expression of another gene

epistasis

Labrador coat color

epistasis

E = (Labrador coat color)

pigment present

e= (labrador coat color)

no pigment present

Two or more genes contribute to one phenotype

polygenic inheritance

Traits influenced by genes + environment

multifactoral

nutrition affects height; sunlight affects skin tone

multifactoral

Family tree tracing inheritance across generations

pedigree

what are squares in pedigrees

males

what are circles in pedigrees

females

heterozygous, phenotypically normal but carry the allele

carriers

what disease poses an advantage to be a carried and what is it an advantage for

sickle cell; malaria

Caused by rare dominant alleles

dominant disorders

: Huntington's disease

dominant disorder

Uses Mendelian principles to estimate risks for future offspring

genetic counseling

Two alleles for a trait separate during gamete formation; each gamete gets one

law of segregation

Genes for different traits segregate independently

law of independent assortment

Round yellow × wrinkled green peas

independent assortment

The "father of genetics"; used garden peas to study inheritance patterns using the scientific method.

gregor mendel

A heritable feature that varies among individuals (e.g., flower color)

character

Each variant for a character

trait

Organisms that produce offspring identical to themselves when self-pollinated

true breeding

Mating of two contrasting true-breeding varieties

hybridization

True-breeding parents in a genetic cross

p generation

Hybrid offspring of the P generatio

f1 generation

Offspring that result when F₁ individuals self-pollinate or cross-pollinate with each other.

f2 generation