BIOL 107 FINAL EXAM

EXAM #5

Life continues through the formation of ________ and _________

new cells and new organisms

Reproduction ensures ____________

survival of species across genereations

Reproduction allows transfer of genetic __________ from ______ → _________

information from parent → offspring

2 Major Strategies of Reproduction

Asexual (clones)

Sexual (genetic variation)

What reproduction do humans use?

BOTH!

our body cells(somatic cells) undergo asexual reproduction – mitosis

The only cells that go sexual reproduction – gametes

DNA contains genes that ________

provide instructions for building proteins

DNA is packaged into __________

chromosomes

_____________ is characteristic for a species

Chromosome number

Humans have ____ chromosomes ( ___ pairs)

46, 23

Diploid (__n)

____ sets of chromosomes

____ set from each ________

Most human cells → ___n = ___

( 2n )

Two sets of chromosomes

One set from each parent

Most human cells → 2n = 46

Haploid (__n)

_____ set of chromosomes

Gametes ( ____ & ____ ) → ___n = ___

( 1n )

One set of chromosomes

Gametes (egg & sperm) → 1n = 23

2n = 4

meanings of 2, “n,” 4

4 = # of total chromosomes

2 = # of sets of chromosomes

n = # of chromosomes per set

Homologous Chromosomes

• same _____

matching pair of chromosomes - one from each parent

• same size, shape, genes/location

In Homologous chromosomes, though they have the same size, shape, genes, locations, they may carry ______ _________/_________

different versions/alleles

karyotype

Image showing chromosomes arranged by size and shape

Karyotype is used to detect

Chromosome number abnormalities result from non-disjunction

(e.g. Down Syndrome)

Structural changes

22 pairs of chromosomes are __________ ____________

2 pairs are ________ _____________

autosomal chromosomes, sex chromosomes

2 Major Phases of cell division

Interphase (G1, S, G2)

M phase (Mitosis + Cytokinesis)

Cells spend most of their time in _________

interphase

Cell division is regulated by ___________

internal checkpoints

Checkpoints make sure that the _______________ for the cell to _______________

right conditions exist for the cell to go through cell division

Interphase

Preparing for division

G1 phase:

• Cell grows

S phase:

• DNA replication → chromosomes duplicated

G2 phase:

• Final growth

• Checks for DNA errors

• Chromosomes are duplicated but not yet condensed

G1 Phase in Interphase

cell grows

S phase

DNA replication → chromosomes duplicated

G2 phase

Final growth

Checks for DNA errors

Chromosomes are duplicated but not yet condensed

Mitosis and Cytokinesis

Produces _________

Mitosis = division of the nuclear contents

Cytokinesis = division of the cytoplasm

• Produces two identical daughter cells

Why cells perform mitosis

• Growth and development

• Tissue repair/healing

• Asexual reproduction (in some organisms)

Purpose of Mitosis

Maintains chromosome number

(2n → 2n)

Phases of Mitosis

Interphase, Prophase, Metaphase, Anaphase, Telophase, Cytokinesis

Interphase - Mitosis

DNA was replicated

Prophase - Mitosis

Chromosomes condense; spindle aparatus develops/forms

Nuclear envelope breaks down

Centrosome (pair of centrioles), move towards opposite ends of the cell

Mitosis - During prophase, centrosomes(pair of centrioles) move toward _____________

opposite ends of the cell

Prometaphase - Mitosis

(spindle apparatus attaches to condensed chromosomes)

Metaphase - Mitosis

chromosomes line up at the cell’s equator

Anaphase - Mitosis

sister chromatids separate and move to opposite poles

Mitosis - During anaphase, sister chromosomes _______ and move to _________?

separate, opposite poles

Telophase - Mitosis

Chromosomes decondense, new nuclei form

cleavage furrow

reverse of prophase

During telophase, chromosomes ______ and new _______ form

decondense, nuclei

Cytokinesis

cytoplasm divides; producing two daughter cells

What does cytokinesis produce?

two daughter cells

Key features of mitosis

Produces 2 genetically identical cells

Diploid → diploid

1 round of cell division

No homologous chromosome pairing

No crossing over

Mitosis has no __________ and no _________

homologous chromosome pairing, crossing over

Why does sexual reproduction requires meiosis?

Reduces chromosome number (diploid → haploid)

Produces gametes (egg & sperm)

Increases genetic variation

Meiosis increases genetic variation through:

Crossing over

Independent assortment

Random fertilization

Mitosis makes _____ cells

somatic cells(body cells)

*makes MY TOES*

Meiosis makes ______

gametes (reproductive/sex cells)

*makes ME*

Crossing over - 3 steps

1. Homologous chromosomes pair up in synapse

2. DNA exchanged through crossing over

3. Produces recombinant chromosomes

Meiosis Phases

Interphase, Meiosis I, Meiosis II

Meiosis I

separation of ______

_______ reduces ( __ → __ )

Separation of homologous chromosomes

Ploidy reduces (diploid → haploid)

Prophase I, Metaphase I, Anaphase I, Telophase I & Cytokinesis

Prophase I - Meiosis I

homologous chromosomes pair (snapsis); crossing over occurs

2n

Metaphase I - Meiosis I

tetrads align at metaphase plate 

Anaphase I - Meiosis I

homologous pairs separate

Telophase I & Cytokinesis - Meiosis I

2 cells, each haploid, form; chromosomes still duplicated

Sister chromatids *no longer identical due to crossing over

Meiosis I produces 

two haploid cells that are genetically unique from the original parent cell

Meiosis II is a separation of ______________

sister chromatids

Meiosis II

Similar to meiosis

Sister chromatids separated → 4 haploid cells

Each gamete is genetically unique

• essentially mitosis for a haploid cell

Meiosis II produces 

four genetically unique haploid daughter cells from the two haploid cells that entered the stage

purpose of mitosis

growth/repair

purpose of meiosis

gamete production

Reproductive System is responsible for:

Production of gametes

Protection/nourishment of developing fetus (in females)

Releasing hormones

Sexual maturity occurs between

8-13 in females

9-14 in males

Production of human somatic cells

• produces _____ cells and _________

• ______ cell division

• produces 2 ____________

• ______ chromosomes in human somatic cells

Mitosis

Produces somatic (body) cells AND diploid germ cells

One cell division

Produces 2 genetically identical, diploid (2n) cells

46 chromosomes in human somatic cells

Production of human somatic cells produces

2 genetically identical, diploid (2n) cells

Production of human sex cells

• produce ________ cells

• involved in _________

• _____ cell divisions (________)

• produces 4 __________

• _____ chromosomes in human gametes

Meiosis

Produces sex cells (gametes)

Involved in sexual reproduction

Two cell divisions (Meiosis I & II)

Produces 4 genetically unique, haploid (1n) cells

23 chromosomes in human gametes

Fertilization

Restores the diploid state

Produces a zygote

Formed when a sperm cell (1n) fertilizes an ovum (1n)

Contains a complete set of chromosomes (2n) – half from each parent

Fertilization restores the _________

diploid state

Fertilization produces ___________

zygote

Fertilization is formed when ______________

Formed when a sperm cell (1n) fertilizes an ovum (1n)

Fertilization contains __________

a complete set of chromosomes (2n) – half from each parent

Zygote

Represents the first cell of new organism

Undergoes rapid cell division (cleavage) to begin embryonic development

Cleavage

rapid cell division – the cells are dividing without really growing in between

Female reproductive organs

Ovaries, Oviduct (fallopian tube), Uterus, Cervix

Ovaries

Produce hormones and oocytes, immature eggs

Oviduct (fallopian tube)

Transport oocyte to uterus

Site of fertilization

Uterus

Muscular organ

Supports embryo development

Walls include:

• Myometrium = muscular layer

• Endometrium = inner lining; thickens and sheds during menstrual cycle

Myometrium

muscular layer in the walls of uterus

Endometrium

inner lining of the uterus; thickens and sheds during menstrual cycle

Cervix

Gateway between uterus and vagina

Oogenesis

development of the ovum

Oogenesis: Before birth

Oogonia → primary oocytes

Primary oocytes begin meiosis I and arrest in prophase I

~1–2 million present at birth

Oogenesis: At puberty

Monthly hormonal signals resume meiosis I

Primary oocyte → secondary oocyte + first polar body

Oogenesis: Ovulation

Secondary oocyte is released

Arrested in metaphase II until fertilization

Oogenesis: If fertilization occurs

Meiosis II completed

Secondary oocyte → ovum + second polar body

Pronuclei fuse → zygote

Follicle

Small, fluid-filled structure that houses and supports a developing oocyte until ovulation

the Ovarian follicle is one of the main places of __________________

estrogen production

Functions of follicle

Protects developing oocyte

Responds to FSH and produces estrogen

Matures the oocyte

Ruptures and turns into corpus luteum

Menarche

First menstruation

Between age 10-16

At birth, a female is born with ______ “____” cells they will ever produce

→ which is about ___________

ALL, “egg”

→ 1-2 million primary oocytes

At puberty, about ________________ oocytes remain

300,000-400,000

Menopause

End of menstrual cycle

Usually occurs in early 50’s when ovaries produce less estrogen and progesterone

Fertility ends when menstrual cycle permanently stops

from menarche to menopause, About ___________ oocytes ovulates

400,000

Ovarian cycle is the development of _______

oocytes

Ovarian cycle

describes monthly changes that occur in ovaries to produce and release an oocyte

Ovarian cycle phases

Follicular phase (~ days 1-14)

Ovulation (around day 14)

Luteal phase (~ days 15-28)

follicle → produces ___________

corpus luteum → produces __________

estrogen,

progesterone

If fertilization occurs, then corpus luteum __________ & progesterone __________

remains, stays up

Menstrual phase ( Day____ )

(Day 1)

Shedding of endometrium

Low estrogen and progesterone

Proliferative phase ( Days ______ )

(~Days 6-14)

Estrogen from growing follicles rebuilds and thickens endometrium

Ends with ovulation

Progestational/Secretory phase ( Days ______ )

(~Days 15-28)

Progesterone from corpus luteum thickens & maintains endometrium

If no fertilization → hormone levels fall menstruation begins

If no fertilization during the progestational phase, hormone levels _________ and ___________

fall, menstruation begins