STUDY GUIDE Mendelian Genetics --- Chapter 6 & 7

• List the genotypes of individuals who have an autosomal dominant trait

AA, Aa

• List the genotypes of normal individuals who do not have an autosomal recessive trait

AA, Aa

• What is a pedigree? Why are pedigrees useful?

A series of symbols are used to represent different aspects of a pedigree. they are useful because they can show us our genetic family history and how the trait could be passed on through generations.

• What is the difference between homozygous and heterozygous genotypes?

a homozygous genotype will have alleles that are either both dominant or both recessive. And a heterozygous genotype will have one dominant and one recessive allele and its phenotype will be dominant.

• What is a test cross? You can find the answer in the textbook!

a cross between an organism with the recessive phenotype and and organism with an unknown phenotype

• What are traits?

a distinguishing quality or characteristic, typically one belonging to a person

• Describe a dihybrid cross

similar to monohybrid cross except that the parents of the first generation differ in two traits

• What is meant by a "carrier"?

you do not show the trait but you can pass it on

• Describe the genotypes/phenotypes of the parents of an individual who is affected by an autosomal recessive trait?

you would either have two heterozygous parents; or one homozygous recessive parent and one heterozygous parent

• Describe an example of incomplete dominance and list genotype and phenotype ratios

• Ex. In certain flowers, R is the allele for red color and r is the allele for white. The Rr flowers will be pink (an intermediate between red and white)

• Describe an example of a trait with multiple alleles and list genotype and phenotype ratios

• Ex: Human blood types: • IA - "A" allele • IB - "B" allele • i - "O" allele Phenotype Possible A, B, AB, O IAIA or IAi, IBIB or IBi, IAIB, ii

• What are polygenic traits? How are these inherited? Describe an example

• Many genes coding for one trait • Some traits are influenced / controlled by multiple genes. • The combination of all of the alleles present in the individual determine the phenotype. • Therefore, these traits are sometimes described as additive. • Many of these traits are distributed along a bell curve in a population. • Ex: height, skin color, eye color

• Differentiate between dominant and recessive alleles

Dominant alleles are always expressed in the organism, while recessive traits tend to be expressed only when the dominant allele is not present.

• List the genotype of an individual who is affected by an autosomal recessive trait

aa

• What are the genotypic and phenotypic ratios when two true breeding plants are crossed?

if you bred two plants that were homozygous dominant and homozygous recessive then the genotype will be 100% heterozygous (Letter letter) and the phenotype will be 100% dominant trait

• What is the purpose of a Punnett square?

used to make predictions about the likelihood of certain traits occurring in offspring based on the genetics of the parents.

• How does environment effect genotype expression?

what you eat can effect you height and the amount of sun recieve will effect your skin color

• If one parent has a homozygous dominant genotype, what are the chances of producing an offspring that shows the recessive phenotype (regardless of the genotype of the second parent)?

100%

• Describe Mendel's Law of Independent Assortment

When gametes form, different genes separate (segregate) independently of each other

• What is a true breeding or purebred organism?

an organism that always passes down certain phenotypic traits (i.e. physically expressed traits) to its offspring.

• What happens in co-dominance?

in co dominance the two traits are both dominant and the end result is a display of both traits at the same time.

• How is co-dominance different from complete (Mendelian) dominance

in co dominance there are 2 dominant traits that show up at once instead of one trait taking over.

• Compare and contrast traits determined by multiple genes vs multiple alleles.

traits caused by multiple genes present phenotype possibilities where the trait can show up in a variety of ways. traits caused by multiple alleles have multiple phenotypes possible but not as many as multiple genes

• What are Mendelian traits?

traits which follow Mendel's rules of only 2 possible versions of a gene (1 dominant, 1 recessive)

• Describe the genotypes/phenotypes of the parents of an individual who is affected by an autosomal dominant trait?

At least one parent will have the trait their genotype could be either AA or Aa. and their phenotype would be that they have the trait present

• Describe an example of a sex-linked trait and list genotype and phenotype ratios

Colorblindness Genotype: XcY : XCY : XCXC : XcXc : XCXc phenotypes: colorblind male : normal male : normal female : colorblind female : carrier

• Describe the genotypes/phenotypes of the parents of a female who is affected by an X-linked recessive trait/disease?

Either the mom will pass it onto the son meaning she is either homozygous recessive or heterozygous; or if it is a daughter, both the mom and dad will have give the daughter the recessive trait

• Describe the relationship between a phenotype and a genotype

The genotype of an organism is defined as the sum of all its genes. The phenotype of an organism is the observable physical or biochemical characteristics of an organism, determined by both genetic make-up and environmental influences

• What is a cross?

The mating of two organisms

• What are the genotypic and phenotypic ratios when two plants that are homozygous dominant for a trait are crossed?

genotype: 100% dominant (Letter Letter) Phenotype: 100% dominant trait

• How is incomplete dominance different from complete (Mendelian) dominance?

in complete dominance if the 2 alleles are heterozygous then the dominant allele will show up for the phenotype. But in incomplete dominance neither the dominant or recessive trait will be present, instead a mixture of the two will be present

• How would you identify a pedigree showing an X-linked recessive trait?

it will show up commonly in males

• What are alleles? Where are they found?

one of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome

• What symbol is used for male? For females? For marriages? To show offspring? To determine age? To show generations? To show someone has a trait? To show a carrier?

A circle represents a female. A square represents a male. A horizontal line connecting a male and female represents a marriage. A vertical line and a bracket connect the parents to their children. A circle/square that is shaded means the person HAS the trait. A circle/square that is not shaded means the person does not have the trait. Children are placed from oldest to youngest.

• Describe an example of codominance and list genotype and phenotype ratios

• Ex: In certain horses and cattle, the alleles for coat color are CR (red) and CW (white). Neither allele is dominant over the other. • CRCR has a red coat • CWCW has a white coat • CRCW has a roan coat (individual hairs may be either red or white, mixed together throughout the coat).

• How do multiple alleles for a gene affect traits?

• Some traits have more than two possible alleles that contribute to the genotype and phenotype. • When there are more than two alleles, multiple phenotypes are possible.

• What happens in incomplete dominance?

• The heterozygote - individual with one dominant and one recessive allele for the trait - displays a phenotype (physical appearance) that is a blending of the dominant and recessive alleles

• How is a sex linked trait inherited? Who inherits it?

A sex-linked trait is inherited from your parents (mom: XX, dad: XY) If you are female, you receive an X from both your mom and dad and you also receive any trait that is include on their X chromosome If you are male you receive one X from your mom and one Y from your dad and you get any trait that is included on their X or Y chromosome

• What are the genotypic and phenotypic ratios when two plants that are homozygous recessive for a trait are crossed?

Genotype: 100% recessive (letter letter) Phenotype: 100% recessive trait

• What are the genotypic and phenotypic ratios when two plants that are heterozygous for a trait are crossed?

Genotype: RR : Rr : rr 1 : 2 : 1 Phenotype: Dominant trait : Recessive trait 3 : 1

• Distinguish among homozygous dominant, heterozygous, and homozygous recessive genotypes

Homozygous dominant: both alleles are dominant, genotype is dominant (RR) Heterozygous: one allele is dominant and one is recessive, its phenotype is dominant (Rr) Homozygous recessive: both alleles are recessive, phenotype is recessive (rr)

• How would you identify a pedigree showing an autosomal dominant trait?

If it is a 50/50 ratio between men and women the disorder is autosomal. Determine whether the disorder is dominant or recessive. If the disorder is dominant, one of the parents must have the disorder.

• What is a karyotype? What is its purpose?

Karyotype is a test to identify and evaluate the size, shape, and number of chromosomes in a sample of body cells. Extra or missing chromosomes, or abnormal positions of chromosome pieces, can cause problems with a person's growth, development, and body functions. Its purpose is to identify any abnormalities on your chromosomes

• Describe the steps of the three experiments Mendel performed using a single trait in pea plants. Explain the results of the experiments using genotype and phenotype ratios for P, F1 and F2 generations. Summarize the results of each step and explain the reason for each outcome generations; Summarize the results of each step and explain the reason for each outcome

Mendel's Experiments Step One: Mendel allowed plants to self-pollinate for several generations to make sure that they were "pure", or true-breeding for flower color. Today, we describe each of these "pure" plants as homozygous. Step Two: Mendel took two pure flowers (one purple and one white), cross-pollinated them. He called these two flowers the P generation (P for parental). Results: All offspring were purple; he called these offspring the F1 generation (F1 for first filial) Step Three: Mendel allowed the F1 flowers (which were all purple) to self-pollinate. The new offspring were called the F2 generation (second filial generation). Results: Roughly 3 out of every 4 (75%) flowers was purple and 1 out of every 4 (25%) was white.

• Describe Mendel's Law of Segregation

When gametes (eggs and sperm) form, the two alleles for each gene separate (segregate) from each other

• List all the genotypes of all normal individuals who are unaffected by a sex-linked recessive trait

XCXc : XCXC : XCY

• List the genotypes of all individuals who are affected by a sex-linked recessive trait

XcXc : XcY

• Describe the genotypes/phenotypes of the parents of a female who is a carrier of an X-linked recessive trait/disease?

You will get one dominant allele from one parent and a recessive allele from the other parent

• List the genotype of normal individuals who do not have an autosomal dominant trait

aa

• What types of disorders can you track with a pedigree?

autosomal dominant, autosomal recessive, x linked recessive, x linked dominant, y linked traits

• What is the difference between an autosomal gene and a sex-linked gene?

autosomal genes are included in the first 22 chromosomes. and a sex linked chromosome is only on the 23 chromosome (X and Y)

• How is the inheritance of autosomal traits different from the inheritance of sex-linked traits?

autosomal traits are more likely to appear especially in both genders where as sex-linked traits are less common and show up more in males

• Why do X-linked recessive traits/diseases affect mostly males?

because in females there are two X chromosomes so if you get on X chromosome with the trait you could still have your other X chromosome be normal; where as in males if you receive a X chromosome with the trait from your mom then you cant prevent yourself from getting the trait because you will receive a Y chromosome from your dad

• On which chromosomes would you find a gene for an X-linked trait? Y-linked trait?

chromosome 23

• On which chromosomes would you find a gene for an autosomal dominant/recessive trait?

chromosomes 1-22

• What is a gene?

the basic physical and functional unit of heredity

• What is a genome?

the complete set of genes or genetic material present in a cell or organism.

• How would you identify a pedigree showing an autosomal recessive trait?

the disorder will commonly skip generations because both alleles have to be recessive.

• What do the letters on the inside (of the boxes) in a Punnett square indicate?

the letters on the inside of the box represent the possible outcomes for the offspring

• What do the letters on the outside (of the boxes) in a Punnett square indicate?

the letters on the outside of the box represent the parents

• What is probability?

the likely hood of an event occurring. in mendelian genetics it is the likely hood of the traits for your children.

• Describe the genotypes/phenotypes of the parents of a male who is affected by an X-linked recessive trait/disease?

the mom will either have the trait or she will be a carrier

• Describe a monohybrid cross

the offspring of homologous parents that differ on a single trait are bred to come up with the second generation

• What is heredity?

the passing on of physical or mental characteristics genetically from one generation to another.

• What is genetics?

the study of heredity and the variation of inherited characteristics