Biology Exam

A. Could a man with blood type A and a woman with blood type B have a child with blood type

yes - only if they both carry a "i" as their second allele.

Law of segregation

alleles for a trait separate (or segregate) from each other during meiosis so that each gamete carries only a single copy of each gene.

genotypic ratio

ratio of possible genotypes for offspring that you could get from crossing two particular parents.

Genetics

scientific study of heredity.

What is the percent chance that they will have a son with hemophilia?

(IF you are calculating this for IF they have a son - then it would be 50%. If you were saying each time they have a child, then there is a 25% chance that they will have a son and that he will be a hemophiliac....)

Describe two examples of polygenic traits in humans. How can you easily tell which traits are polygenic? (how will they appear?)

(how will they appear?) hair color or skin color - they appear in a range of shades from very dark to very light. This tells you that there is more than one gene involved in determining the appearance of this trait and that whatever combination you get determines your specific shade.

Blood types are an example of a multiple allele trait. List all the genotypes for each blood type below: A IAi, or IAIA B IBi or IBIB O ii AB IAIB Circle the phenotypes above that have more than one genotype.

(type A and type B have two possible genotypes)

Mendel

- The "Father of Genetics" - his experiments with pea plants led to certain scientific laws about how traits are passed on from parent to offspring. His laws still hold true today and are the basis of our modern understanding of genetics.

pedigree

- chart that shows the relationships within a family. Can also be used to demonstrate how genetic traits have been carried through the generations. It is helpful in determining modes of inheritance for traits and individuals genotypes.

Describe the following inheritance patterns, write out an example of how you would write the genotype and give an example of an organism that displays this type of inheritance. Codominance

- in the heterozygous individual, both alleles are present, but separate in the phenotype. For example, a speckled chicken would have both black and white feathers if they have both alleles. o Could be written as two different letters, both capitalized, or it could be written as two different letters that are superscript. For example - "C" is the trait - chicken color. Cw = allele for white feathers, CB = allele for black feathers

haploid

- term used to refer to a cell that contains only a single set of chromosomes and therefore only a single set of genes. (ex. Gametes, or sex cells, only have 1 chromosome in each pair. )

Circle all that is true of a homologous pair of chromosomes: a. They are the same size b. they have the same genes in the same location c. They have the same alleles for a gene

A & B

What kind of disorders can you see in a karyotype?

A chromosome number disorder (such as the ones listed in #14) or a disorder in which a large part of the chromosome is missing. You can NOT see what alleles a person has on their chromosomes - so mutations of a single gene would be impossible to diagnose with this tool. (such as sickle cell anemia, hemophilia, albinism, etc.)

How is a monohybrid cross different from a dihybrid cross?

A monohybrid cross shows the inheritance of ONE trait, while the dihybrid cross shows the inheritance of TWO traits at the same time.

2. Circle each phrase below that a Punnett Square CAN show. a. The alleles in the gametes of each parent b. The actual results of a genetic cross (i.e. - the actual children that these two parents produce) c. The alleles for one trait in an offspring d. The genotypes of all possible offspring that can be created by these two parents e. The possible results of a genetic cross between two parents. f. ALL the alleles for every trait in the offspring.

A, C, D, & E

Circle ALL statements below that are true of genetic disorders: A. Sickle Cell Anemia is most prevalent in Asian Americans. (not true - more common in races from tropical areas like Africa.) B. Cri du Chat is characterized by a cat-like cry. C. Down syndrome results in mental retardation and is caused by an extra 21st chromosome. D. Monosomy and Trisomy disorders cannot be diagnosed from a karyotype. (false - chromosome number disorders CAN be seen on a karyotype.) E. Albinism is an autosomal recessive disorder that results in no skin pigmentation, sun sensitivity, and abnormalities with vision.

B. Cri du Chat is characterized by a cat-like cry. C. Down syndrome results in mental retardation and is caused by an extra 21st chromosome. E. Albinism is an autosomal recessive disorder that results in no skin pigmentation, sun sensitivity, and abnormalities with vision.

What are the genotypic and phenotypic ratios for the offspring of this cross?

Genotypic ratio: 0 SS: 0LL: 4 LS (or 100% LS) Phenotypic ratio: 4 medium: 0 short: 0 long (100% medium-legged cats)

What are the probable genotypic and phenotypic ratios for the offspring of this cross?

Genotypic ratio: 1 XHXH : 1 XHXh : 1 XHY : 1 XhY

Hemophilia is a recessive sex-linked disorder. A normal man marries a woman who is a carrier of the disorder. What are the parents genotypes? (remember that if this is sex-linked, the alleles have to be written correctly)

If H = normal and h = hemophilia, then the woman would be XHXh, and the man would be XHY

parental & filial generations

In Mendel's experiment, he named the first generation of plants he experimented with the "p" generation. The children of "P" were called "F1" - "F" stands for filial, which means "son or daughter" in Latin. The "F2" generation would have been the children of F1.

A cat with long legs was mated to a cat with short legs. All of the offspring had medium-length legs. What is the name given to this pattern of inheritance?

Incomplete dominance (it is a BLEND of the two alleles)

Draw a punnett square demonstrating the cross between the cats in question #4.

LS LS LS LS

nondisjunction

Nondisjunction is when homologous chromosomes fail to separate during meiosis. This results in two gametes with too many chromosomes and two with not enough chromosomes.

Hemophilia is a recessive sex-linked disorder. A normal man marries a woman who is a carrier of the disorder. Show the punnett square for this cross: H = normal and h = hemophilia, then the woman would be XHXh, and the man would be XHY

Punnett Square: XH Xh XH XHXH XHXh Y XHY XhY

Hemophilia is a recessive sex-linked disorder. A normal man marries a woman who is a carrier of the disorder. Which chromosome usually carry sex-linked genes?

The X chromosome - it is much larger than the Y and carries many more genes. Everyone has an X chromosome - only males have a Y.

Explain why men determine the sex of offspring?

They are the only one who has a Y to give away. Females just have two x's.....

monohybrid cross

a cross in which you are studying only ONE trait. This is what a "normal" 2 x 2 punnett square shows. (a dihybrid cross would show the alleles for TWO traits and would require a 4 x 4 punnett square (pg. 270))

When a man's normal sperm cell fertilizes a woman's normal egg cell, a. how many total chromosomes will be found in the zygote? b. how many total sex chromosomes will be found in the zygote? c. how many total autosomes (body chromosomes) will be found in the zygote? d. how many total chromosomes did each parent contribute to the zygote?

a. 46 b. 2 c. 44 d. 23

Give three examples of genetic disorders that can result from nondisjunction and tell what chromosome pair would be affected in each.

a. down's syndrome - trisomy 21 b. klinefelter's syndrome - trisomy of the sex chromosomes (XXY) c. turner's syndrome - monosomy of the sex chromosomes (X and no other sex chromosome).

Could a man who has AB blood a. father a child with O blood? b. father a child with A blood? c. father a child with B blood?

a. no b. yes c. yes

Recessive

an organism with a recessive allele will only exhibit that form of the trait if no dominant alleles are present. (must be homozygous recessive to have the recessive phenotype).

What is a mutation?

change in a DNA sequence that affects the genetic information. (can be a source of genetic variation.)

DNA

deoxyribonucleic acid - nucleic acid that contains the sugar deoxyribose. (contains all the instructions for making proteins needed by an organism)

Punnett square

diagram showing the gene combinations that might result from a genetic cross. (Doesn't show actual results - every time sexual reproduction occurs, it is random which sperm fertilizes the egg and which chromosomes end up in each gamete.)

genotype

genetic makeup of an organism. For each trait, the "genotype" would be written as two letters that represent the two alleles that you have for that particular trait. Ex. Tt or tt

Describe the following inheritance patterns, write out an example of how you would write the genotype and give an example of an organism that displays this type of inheritance. - Strictly dominant/recessive

if you have at least one dominant allele, then you will have the dominant phenotype. Ex. In Mendel's experiment, the trait for tall plants was dominant to short plants. If plants had at least one tall allele, then they would be tall. Would be written as a capital and a lowercase letter. Ex. T = tall, t = short. Genotypes for plant height could be TT, Tt, or tt

Incomplete dominance

in the heterozygous individual, the alleles are blended in the phenotype. For example, snapdragons have an allele for red flowers and an allele for white flowers. If the plant has both alleles, it will end up being pink. o Written in the same way as codominance.

What is the picture called that shows homologous pairs of chromosomes in order from largest to smallest, with the sex chromosomes last?

karyotype

probability

likelihood that a particular event will occur.

Allele

one of a number of different forms of a gene. For example, for the trait of hair color, you might have the alleles for brown hair, red hair, black hair, blonde hair, etc.

phenotype

physical characteristics of an organism. Ex. Tall, brown hair, blue eyes, etc.

gene

sequence of DNA that codes for a protein and thus determines a trait

gamete

specialized cell involved in sexual reproduction.

Trait

specific characteristic that varies from one individual to another.

Law of independent assortment

states that genes for different traits can segregate independently during the formation of gametes. (i.e. the way alleles for one trait are inherited does not affect which alleles you get for another trait. The only exception to this rule is if alleles for multiple traits are close together on the same chromosome. )

Law of dominance

states that some alleles are dominant and others are recessive. (if you have at least one dominant allele, then you will end up with the dominant phenotype.)

Dominant (principle of dominance)

states that some alleles are dominant and some are recessive. If an allele is dominant, then an organism will have that form of the trait if they have at least one dominant allele.

diploid

term used to refer to a cell that contains both sets of homologous chromosomes. (i.e. - two chromosomes in each pair of chromosomes - ex. Body cells are diploid. Each set of chromosomes has one from the egg and one from the sperm. )

Heterozygous

term used to refer to an organism that has two different alleles for the same trait.

Homozygous

term used to refer to an organism that has two identical alleles for a particular trait.

Heredity

the passing on of genes and genetic traits from parent to offspring

phenotypic ratio

the ratio of possible phenotypes in offspring that you could get from two particular parents.

Multiple allele traits

this trait has only ONE gene (so you only get two alleles) but there are several choices for the alleles that you could get. Example - in bunnies, there are alleles for hair color that include himilayan, chinchilla, albino, brown, etc. see page 273 for example and how to write genotype.

Polygenic traits

this trait will have more than one gene involved in determining the outcome of the phenotype. It will appear on a scale of shades or types. For example, skin color ranges from very dark to very light. o Written as several genotypes together: AABbCc