Ch 9 Sexual Reproduction and Meiosis (unfinished)

Asexual Reproduction

One parent organism replicates its DNA and splits the contents of one cell into two. This creates two genetically identical offspring. 

What organisms generally reproduce asexually

Unicellular Organisms

Sexual Reproduction

The DNA of the offspring comes from two parents. An egg fuses with a sperm, yielding the first cell of the offspring.

What organisms generally reproduce sexually

Multicellular Organisms

Why is Sexual Reproduction beneficial

Sexual reproduction produces genetic diversity among offspring, which increases the chance that some offspring survive in changing environments.

Homologous Chromosomes

 Matching pairs of chromosomes that carry the same genes in the same order.

Diploid Cells 

Cells with two sets of Chromosomes (Chromosomes from Mom and Dad) 

Karyotype

All of the chromosomes from a diploid human cell.

Human cells contain how many homologous sets of chromosomes

23

Human cells contain how many homologous sets of autosomes

22

Autosomes

The numbered chromosomes. These chromosomes are the same for both biological males and females

Human cells contain how many sets of sex chromosomes

1

Alleles

Which are alternative versions of the same gene.

Chromatids

When members of a homologous pair are replicated, identical alleles are on sister…

Haploid

Cell has only one set of chromosomes.

Zygote

The first cell of a new organism.

Zygotes grow and develop by

Mitosis

In adults, specialized diploid cells called

germ cells

Independent assortment

Chromosome pairs align randomly, scrambling the combination of chromosomes for each gamete

Whats the difference between Diploid and Haploid cells

Haploid cells have one copy of each chromosome while Diploid have two copies of each chromosome

Nondisjunction

If chromosomes fail to separate properly, abnormal gametes form.

Triple-X syndrome

Tall stature, menstrual irregularities, increased risk of giving birth to triplo-X daughters or XXY sons

Klinefelter, or XXY, syndrome

Variable, but often include sexual underdevelopment, long limbs, large hands and feet, development of breast tissue

Jacobs, or XXY, syndrome

Often few noticeable symptoms; tall stature, acne, problems with speech and reading

Turner syndrome

Short stature, sexual underdevelopment, infertility

Prophase I

: Homologous chromosomes pair up and attach to the spindle

Metaphase I:

Homologous chromosomes line up in two rows

Anaphase I:

Homologous chromosomes separate

Telophase I:

Chromatids remain together

Prophase II

Chromosomes attach to spindle

Metaphase II

Chromosomes line up in one row

Anaphase II:

Chromatids separate

Telophase II:

Four new cells each have one set of chromosomes

crossing over

 two homologous chromosomes pair up and exchange pieces, scrambling the genetic material. 

independent assortment,

chromosome pairs align randomly, scrambling the combination of chromosomes for each gamete.

How many chromosome combinations are possible in metaphase I arrangement?

2²³ = 8,388,608

Monozygotic twins are genetically

Identical. An embryo splits in two. Each embryo then develops independently.

Fraternal twins

two sperm cells fertilize two separate egg cells, and the offspring might look very different.

 nondisjunction.

If chromosomes fail to separate properly, abnormal gametes form.

Spermatogenesis produces _______ sperm cells for each germ cell

four

Oogenesis produces ____ egg cell for each germ cell

one