State AssessmentLife Sciences

S.HS. 3.2.3All questions taken from California

Dept. of Ed. Released Test Questions 2007

Mitosis & Meiosis

• Mitosis produces 2 body cells that are diploid (containing a complete set of chromosomes) body cells; these cells are made for the purpose of growth and repair

• Meiosis produces gametes (sex cells) and is responsible for 4 haploid cells; when the four haploid cells are produced

A. Prophase I of Meiosis is responsible for genetic recombination due to crossing over of homologous chromosomes.

Genetics Question #1

• Which of the following best describes meiosis?

A It occurs only in cells in the reproductive structures of the organism.

B It is carried out in tissues that require cell replacement.

C It happens in tissues except the brain and spinal cord.

D It is the first stage of mitosis.

Genetics Question #2

• The diagram to the left shows homologous chromosomes during prophase I of meiosis. Which of the following correctly describes the process being illustrated?

A mutation in which the DNA content of the gene is altered

B segregation of sister chromatids

C condensation and segregation of alleles

D crossing-over in which alleles are exchanged

Genetics Question #3

• Mendel hypothesized that reproductive cells have only one factor for each inherited trait. This hypothesis is supported by the observation that

A haploid cells are produced by mitosis. B diploid cells are produced by mitosis. C haploid cells are produced by meiosis. D diploid cells are produced by meiosis.

Genetics Background Info. • Chromosomes contain DNA; segments of DNA are called genes• Watson and Crick- determined that DNA was a structure that appeared to be a double

helix. • When looking at genetics several vocabulary terms are important: A. alleles-forms of a gene

1.)homozygous-two of the same forms of a trait (e.g.TT or tt) 2.)heterozygous(hybrid)-two different forms of the trait (e.g. use hybrid cars and Tt)

B. genotype-genetic makeup of an organism (alleles Gg) C. phenotype-physical appearance of an organism (green) D. carrier- individual who carries the trait and can pass the trait to offspring, but they do

not show signs of the trait being demonstrated E. autosomes- in humans the first twenty-two pairs of chromosomes F. sex chromosomes- in humans the twenty-third pair of chromosomes

1.)Males sex chromosomes are XY 2.)Females sex chromosomes are XX

*males can only receive sex linked traits (X linked traits) from their mothers because they receive their Y chromosome from their father and are more frequently colorblind and hemophiliacs because these two disorders are X linked and recessive; females must receive two recessive alleles from both parents to be colorblind or a hemophiliac

Monohybrid Cross• Trait examining one trait of an

organism• The two alleles each parent can

give to offspring must separate as gametes can do this. If one parent has a genotype of Ww and the other parent has a genotype of ww, each of the w’s will separate. A cross can be demonstrated to show probability for offspring genotypes.

W w w

w

Ww ww

Ww ww

Genetics Question # 4

• In mice, the gene for red eyes R is dominant and the gene for sepia eyes r is recessive. What are the possible combinations of genes in the offspring of two red-eyed heterozygous mice (Rr)?

A RR only B rr only C Rr and rr only D RR, Rr, and rr only

Genetics Question #5

• In certain breeds of dogs, deafness is due to a recessive allele (d) of a particular gene, and normal hearing is due to its dominant allele (D). What percentage of the offspring of a normal heterozygous (Dd) dog and a deaf dog (dd) would be expected to have normal hearing?

A 0% B 25% C 50% D 100%

Dihybrid Crosses

• Dihybrid crosses are done when a person is looking at two traits that an organism has and the chances of offspring receiving a particular genotype or phenotype

• Because two traits are involved, each parent has four alleles that sort independently of one another

A. For instance, if a parent has alleles RrYy, the gene combinations can be RY, Ry, rY, and ry B. For roundness, “R” can combine with “Y” and “y”. C. For wrinkledness, “r” can combine with “Y” and “y”.

Genetics Question #6

• If a corn plant has a genotype of Ttyy, what are the possible genetic combinations?

A Ty, ty

B TY, ty

C TY, Ty, ty

D Ty, ty, tY, TY

Dihybrid Cross Implementation• In order to complete a dihybrid

cross you must first have two traits from each parent in order to find offspring using this method.

• If the male’s genotype is RrYy and the female’s genotype is RrYy, then what are the possible phenotypes of their offspring?

• Cross- RrYyX RrYy• Use the FOIL method: first, outer,

inner, last A for the first parent, RY: Ry: rY: ry B for the second parent, RY: Ry:

rY: ryBecause you have four combinations

for each parent,sixteen boxes will be needed

RY Ry rY ry

RY

Ry

rY

ry

Genetics Question #7• Fur color in cats is controlled by

an autosomal gene that can occur in the dominant form, (B), or the recessive form, (b). The length of the cat’s fur is controlled by another autosomal gene that occurs in the dominant form, (S), or the recessive form, (s). The table shows the traits for these allele codes.

BbSs (male) bbSS (female)

The following genotypes were foundin a male and a female cat.BbSs (male) bbSS (female)

Which one of the following choices istrue of the phenotype of offspringfrom these parents?

A All offspring will have black fur.B All offspring will have white fur.C All offspring will have long-haired

fur.D All offspring will have short-haired

fur.

Genetics Question #8

• The chart to the left shows four alleles at the same locus that affect rabbits’ coat color. Each allele is dominant to the ones below it. Rabbits with an albino or Himalayan coat are more susceptible to predators. Which of the following genotypes will produce a rabbit that is least likely to survive?

A cchcB CcC chcD Cch

Genetics Question #9

• In pigeons there is a rare inherited condition that causes the death of chicks before hatching. In order for this disease to be passed from generation to generation there must be parent birds that

A are heterozygous for the disease. B have the disease themselves. C produce new mutations for this disease. D are closely interbred.

Genetics Question #10

• A healthy individual is a carrier of a lethal allele but is unaffected by it. What is the probable genotype of this individual?

A two dominant normal allelesB one recessive lethal allele and one dominant lethal alleleC one recessive lethal allele and one dominant normal alleleD one dominant lethal allele and one recessive normal allele

Genetics Question #11• The diagram below shows Rosalind Franklin’s x-ray diffraction image of

DNA.

How did this evidence affect the work of Watson and Crick?

A It was used to determine the physical structure of DNA.B It was used to identify the four bases that make up DNA.C It was used to develop the theory of independent assortment.D It was used to show that DNA was the molecule of inheritance.

Genetics Question #12

• If a human baby boy inherits a recessive allele from his mother, in which circumstance would he most likely show the trait?

A The baby inherits the dominant allele from his father.B The allele is on an autosomal chromosome and the baby is a twin.C The allele is on the X chromosome.D The allele is on the Y chromosome.

Slide Answers

• #1 A• #2 D• #3 C• #4 D• #5 C• #6 A

• #7 D• #8 C• #9 A• #10 C• #11 A• #12 C