Chapter 7 The Cellular Basis of Inheritance

Introduction and 7.1 Sexual Reproduction

What is a basic characteristic of all living things?

Highlight the correct answer of the choices in parentheses for each statement

The offspring of any organism closely resembles its parents because they reproduce (in kind/exactly the same).

Many single-celled organisms can produce genetically identical clones of themselves through (mitosis/meiosis).

Meiosis leads to (diploid/haploid) cells that are part of the sexual reproductive cycle.

Sexual reproduction introduces (variation/identical traits) into offspring

The use of sexual reproduction in eukaryotes is evidence of its evolutionary (failure/success)

There is (no need/need) to find or attract a mate for sexual reproduction

An (asexual/sexual) population can grow twice as fast, giving them an advantage

(Environment/mutation) is the ultimate source of variation in sexual organisms and the only source in asexual organisms

(Mitosis/Meiosis is the division of the contents of the nucleus that divides the chromosomes among gametes

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Life Cycles of Sexually Reproducing OrganismsUse figure 7.2 (print book) figure 1 in section 7.1 (online book)

What three kingdoms are represented in the figure?a.b.c.

Each of the three portions of the figure is split into two parts. Which part, upper blue or lower purple, is the diploid part of the life cycle?

Follow the overall direction of the arrows. What process moves the life cycle from diploid to haploid?

Continue following the direction of the arrows. What processes move the life cycle from haploid to diploid? Animals and Plants =

Fungus =

Comparing the three kingdoms represented, highlight those that have multicelled diploid bodies. These are called diploid-dominant. (look for the diploid zygote and follow the arrow to see if the zygote goes through mitosis to become multicelled)

Animal Fungus Plant

Comparing the three kingdoms represented, highlight those that have multicelled haploid bodies. They are referred to as haploid-dominant. (look for haploid spores going through mitosis to become multicelled)

Animal Fungus Plant

Comparing the three kingdoms represented, highlight those that have both multi-celled haploid and diploid bodies. Since these are not haploid or diploid dominant, they are referred to as having alternating generations. They alternate between multicellular diploid and haploid bodies.

Animal Fungus Plant

Animal life cycle (diploid-dominant)In the animal diagram, what are the only haploid cells?

Gametes, egg and sperm, are produced by specialized cells called ________ cells. (see paragraph two of this section)

Fungus life cycle (haploid-dominant)What is the only diploid cell in the fungus life cycle?

When the spores divide by mitosis they grow into the main body of the fungus composed primarily of long slender filaments called ______________.

Plant life cycle (alternation of generations)What is the name of the multicelled haploid body in plants?

What is the name of the multicelled diploid body in plants?

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7.2 MeiosisRead through the text, Label the diagram by filling in the empty text boxes.

Answer the following questions and use the indicated answers to correctly label the figure.

What type of cells are the nonreproductive cells in a multicellular organism?

What type of cells are specialized to go through meiosis? Use this answer as the label in both text boxes 1.

The two cells at the top of the figure each have two of the same type of chromosome. Are they diploid (2n) or haploid (n)? Write this in text box 2.

How many cell divisions occur for meiosis?

After the first round of cell division (meiosis I) what happens to the chromosome number in each cell. (Count each duplicated chromosome as 1 chromosome not 2. They have two sister chromatids, but still count as one chromosome.)

Are the cells in the pink box, following meiosis I diploid (2n) or haploid (1n)? Write this in text box 3.

Following meiosis II four cells are produced from each original germ cell. What are these cells called? Write this in both text boxes 4.

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1. 1. 2.

3.

4. 4. 5.

7.

6.

What is the process called when two haploid gametes fuse together? Write this answer in text box 5.

What cell is produced following fertilization? Write this answer in text box 6.

Is the zygote diploid or haploid? Write this answer in text box 7.

Interphase, Meiosis I, and Meiosis II

Match each term with its description

_____ 223 A. Random positioning of maternal and paternal chromosomes at the spindle equator

_____paternal chromosomes B. tight pairing of homologous chromosomes

_____prophase I C. reduction of the parental chromosomal number by half

_____nonsister chromatids D. these break at the same places along their length and then exchange corresponding segments—including genes

_____crossing over E. Four sister chromatids of each pair of homologous chromosomes held together

_____function of meiosis F. orientation of each pair of homologous chromosomes at the center of a cell in metaphase I is random

_____maternal chromosomes G. 23 chromosomes inherited from your father

_____metaphase I H. breaks up old combinations of alleles and puts new ones together in pairs of homologous chromosomes

_____synapsis I. A time of much gene shuffling

_____tetrads J. 23 chromosomes inherited from your mother

_____independent assortment K. possible number of combinations of maternal and paternal chromosomes possible in gametes from one germ cell

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Organize the images into the correct order to represent meiosis.

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Prophase I

Metaphase I

Anaphase I

Telophase I

Prophase II

Metaphase II

Anaphase II

Telophase II

Briefly explain the following methods of increasing variation in offspring from sexual reproduction

Crossing over during Prophase I (examine the figure showing crossing over)

Independent assortment during Metaphase I (examine the figure showing chromosome arrangements)

Examine the figure. Explain why homologous pairs are separated during meiosis I but sister chromatids are separated during meiosis II.

Comparing Meiosis and Mitosis

Read through this section studying the figure to note the differences between the two processes.

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7.3 Errors in Meiosis

Disorders in Chromosome Number: Nondisjunctions, Duplications, and Deletions

Define each of the following:

Nondisjunction

Euploid

Autosomes

Aneuploid

Monosomy

Trisomy

If a nondisjunction occurs at anaphase I of the first meiotic division, what will be the proportion of abnormal gametes (for the chromosomes involved in the nondisjunction)?

If a nondisjunction occurs at anaphase II of the second meiotic division, what will be the proportion of abnormal gametes (for the chromosomes involved in the nondisjunction)?

Choose from the following:A. Down syndromeB. Turner syndromeC. Klinefelter syndromeD. XXY conditionE. XYY conditionF. XXX syndrome

_____ 1. About one of every 500 to 1000 males inherits one Y and two or more X chromosomes, mainly by nondisjunction

_____ 2. Most don’t have functional ovaries and can’t produce enough sex hormones

_____ 3. The testes and the prostate gland usually are smaller than average; hair is sparse, the voice is pitched high, and the breasts are a bit enlarged

_____ 4. Tend to be taller than average, with mild mental impairment, but most are phenotypically normal

_____ 5. Most affected individuals show moderate to severe mental impairment and heart defects; as a group, they tend to be cheerful and sociable people

_____ 6. Occurs at a frequency of about 1 in 1000 live births, adults are fertile; no physical or medical problems

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Disorders in Chromosome Number: Chromosome Structural Rearrangements

Label each of the diagrams of abnormal chromosome structure as a deletion, a duplication, an inversion, or a translocation.

1. ________________ 2. _________________

3. ________________ 4. _________________

Which type of the above rearrangements results in the cri-du-chat syndrome?

What gene is thought to have evolved 350 mya which today determines male sex?

Fill in the numbers in the following statements about human chromosomes compared to chimpanzees

____________ chromosomes are almost identical

____________ chromosomes are similar, except for some inversions

____________ chromosome matches up with ______________ in chimpanzees

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