Biology I Unit 7: Genetics and Heredity

Dihybrid cross

the cross between two different genes that differ into two observed traits.

Monohybrid, dihybrid

_____________________ crosses are 2x2 squares while ______________________ crosses are 4x4 squares.

Using the FOIL method.

How do you determine what genotypes to put on the sides of the Punnett square in a dihybrid cross?

4 tall yellow peas, 4 tall green peas, 4 short green peas, & 4 short yellow peas.

A heterozygous tall, heterozygous yellow pea plant is crossed with a short, green pea plant. Tall is dominant to short (T, t) and yellow is dominant to green (G, g).

Determine the probability of tall yellow, tall green, short yellow, and short green.

25%

If all the genotypes of a dihybrid cross have exactly 4 in each category, what are the probabilities?

Pedigrees

used to analyze the pattern of inheritance of a particular trait throughout a family.

The presences or absence of a trait as it relates to the relationship among parents, offspring, and siblings.

What do pedigrees show?

Determine genotypes, identify phenotypes, and predict how a trait will be passed on the future.

What can you do when analyzing a pedigree?

TRUE

True or False: Pedigrees make it possible to determine how certain alleles are inherited.

Dominant, recessive, autosomal, or sex-linked.

What type of alleles can a pedigree determine?

dominant

If the trait is _________________, one of the parents must have the trait; these traits will not skip a generation.

recessive

If the trait is __________________, neither parent is required to have the trait since they can be heterozygous.

Males

Who is more commonly affected in X-linked recessive traits?

autosomal

In ___________________ traits, both male and female are equally likely to be affected (usually in equal proportions).

Incomplete dominance

situation in which one allele is not completely dominant over another.

Codominance

situation in which both alleles of a gene contribute to the phenotype of the organism.

Incomplete dominance, codominance

A pink flower is an example of __________________________ while a cow with brown and white spots (roan) is an example of _______________________.

Multiple alleles

three or more alleles of the same genes.

Two alleles, one from mother and one from father.

How many alleles can an individual have for a particular trait?

Coloring traits (eyes & hair color)

Multiple alleles is very common for what trait?

Examples of multiple alleles.

Coat color in rabbits, blood type, and hair color.

X and Y

What are the two sex chromosomes that a human could have?

XX, XY

Females have ________ sex chromosomes while males have _________ sex chromosomes.

X-linked traits

What is controlled by genes on the X chromosome?

Males, because they only have one X chromosome while females have two.

Of males and females, who is more likely to inherit the X-linked traits?

Examples of X-linked traits

Colorblindness, balding, and hemophilia.

Polygenetic trait

a trait controlled by two or more genes; often show a wide range of phenotypes.

The wide range of skin color in humans that comes about partly because more than four different genes probably control this trait.

What is an example of a polygenetic trait?

Examples of polygenic traits.

Color of epidermis, texture of epidermis, and blood flow in dermis.