Unit 5

The study of heredity and hereditary variation:

Genetics

The transmission of traits from one generation to the next:

Heredity

Traits are passed from parents to offspring through what?

Genes

Segments of DNA that code for basic units of heredity:

Genes

How do offspring acquire genes from parents?

By inheriting chromosomes

Types of reproduction:

Asexual and sexual

How many individuals perform asexual reproduction?

Single individual

Does asexual reproduction involve fusion of gametes?

No

What are the offspring of asexual reproduction like?

Exact copies of parent

Source of variation of asexual reproduction:

Mutations

What does asexual reproduction occur through?

Mitosis

Who performs sexual reproduction?

2 parents

Sex of the parents performing sexual reproduction:

One male one female

What are offspring of sexual reproduction in relation to parents?

Unique combinations of genes from parents

Offspring from sexual reproduction are genetically the same / varied from parents and siblings

Varied

A pair of chromosomes that carry the same genetic information:

Homologous chromosomes

What is the same about homologous chromosomes?

Size, length, centromere position, genetic information

Who are the homologous chromosomes inherited from?

One from mom and one from dad

A display of chromosome pairs ordered by size and length:

Karyotypes

Is it easy to see the sister chromatids in actual karyotypes?

No

What are somatic cells also called?

Body cells

How many chromosomes do diploid cells have?

2 sets of 23 chromosome

What are gametes also called?

Sex cells

Having 2 sets of each chromosome:

Diploid

Having one set of each chromosome:

Haploid

Gametes in humans:

Eggs and sperm

How is DNA in eukaryotes found?

Packaged in chromosomes

Types of chromosomes:

Autosomes and sex chromosomes

Chromosomes that do not determine sex:

Autosomes

How many pairs of autosomes are found in humans?

22

Sex chromosomes:

X and Y

Sex chromosomes for eggs in humans:

X

Sex chromosomes for sperm in humans:

X or Y

Do all sexually reproducing organisms have a diploid and haploid number of chromosomes?

Yes

Sequence of stages in the reproductive history of an organism from conception to its own reproduction:

Life cycle

What and what alternate in sexual life cycles?

Fertilization and meiosis

When a sperm cell fuses with an egg to form a zygote:

Fertilization

Is a zygote diploid or haploid?

Diploid

A process that creates haploid gamete cells in sexually reproducing diploid organisms:

Meiosis

What does meiosis result in?

Daughter cells with half the number of chromosomes as parent cell

What does meiosis produce in humans?

Sperm and eggs

How many rounds of division does meiosis involve?

2

What are the rounds of division in meiosis called?

Meiosis I and Meiosis II

Where does mitosis occur in?

Somatic cells

What does meiosis form?

Gametes

Number of divisions for mitosis vs meiosis:

1 vs 2

Result of mitosis vs meiosis:

2 diploid daughter cells vs 4 haploid daughter cells

In mitosis, are daughter cells genetically identical or unique?

Identical

In meiosis, are daughter cells genetically identical or unique?

Unique

Key events in meiosis that are unique from mitosis:

Prophase I, metaphase I, anaphase I

Phases of meiosis I:

Interphase, prophase I, metaphase I, anaphase I, telophase I and cytokinesis

What does cell go through during interphase of meiosis I?

G1, S, G2

What happens to DNA during S phase of interphase of meiosis I?

Copied

What occurs during prophase I?

Synapsis and crossing over

What do homologous chromosomes do during synapsis?

Pair up and physically connect to each other

What does homologous chromosomes physically connecting to each other during synapsis form?

Tetrad

What is crossing over also called?

Recombination

Where does crossing over occur?

At the chiasmata

What happens during crossing over?

DNA exchanged between homologous pairs

What does each chromatid produced from prophase I have?

Unique combination of DNA

What happens during metaphase I?

Independent orientation

What happens during independent orientation?

Tetrads line up at metaphase plate

What happens to pairs of homologous chromosomes during anaphase I?

Separate

Are sister chromatids still attached during anaphase I?

Yes

What divides during telophase I and cytokinesis?

Nuclei and cytoplasm

What is there now in each daughter cell after telophase I and cytokinesis?

Haploid set of chromosomes

Phases in meiosis II:

Prophase II, metaphase II, anaphase II, telophase II and cytokinesis

Does crossing over occur during prophase II?

No

What forms during prophase II?

Spindle

What happens to chromosomes during metaphase II?

Line up at metaphase plate

Are chromatids unique at metaphase II?

Yes

Why are chromatids unique at metaphase II?

Because of crossing over in meiosis I

What happens to sister chromatids during anaphase II?

Separate and move towards opposite poles

What does telophase II and cytokinesis result in?

4 haploid cells

What reappears during telophase II and cytokinesis?

Nuclei

Is each daughter cell produced by meiosis II genetically identical or unique?

Unique

Three ways in which meiosis leads to genetic variation:

Crossing over, independent assortment of chromosomes, random fertilization

What does crossing over produce?

Recombinant chromosomes

What do chromosomes do during crossing over?

Exchange genetic material

How are chromosomes oreinted along the metaphase plate during metaphase I?

Randomly

How can each chromosome orient?

With maternal or paternal chromosomes closer to given pole

What does random fertilization mean?

Any sperm can fertilize any egg

What does meiosis followed by fertilization ensure in sexually reproducing organisms?

Genetic diversity

What does meiosis followed by fertilization provide?

Genetic variation

What does the genetic variation provided by meiosis and fertilization play a role in?

Natural selection

What is the cellular process of meiosis driven by?

Interaction of subcellular components

What does meiosis use to drive the cellular process?

Free energy required for growth and reproduction of living systems

What does DNA and RNA carry?

Genetic information

What is the genetic code shared by?

All living systems

What did Gregor Mendel study?

Inheritance

What did Gregor Mendel create?

Two laws that can be applied to study of genetics

Who was Gregor Mendel?

An Austrian monk

What did Gregor Mendel experiment on?

Pea plants

What did Gregor Mendel discover?

Basic principles of heredity

Why did Gregor Mendel experiment on pea plants?

Many varieties, can control mating, relatively short generation time

What characteristics did Mendel track?

Characteristics that came in 2 distinct forms

Examples of characteristics of pea plants that come in 2 distinct forms:

Color (purple or white), seed shape (round or wrinkled)

What did Mendel use to control his experiments?

True breeding plants

Organisms that produce offspring of the same variety over many generations of self pollination:

True breeding

What will true breeding purple pea plants only produce with self pollination?

Purple offspring