Exam 3 - The cell cycle, mitosis, meiosis, Gregor Mendel

______________ are the binding location for ligands

Receptors

What are ligands, give at least 3 examples

- Ligands are signaling molecules (smaller molecules that bind to larger molecules)

- Ex. Gas molecules, lipids, proteins

What is the sequence of cell signaling? (1-3)

1. Reception - ligands bind to receptors

2. Transduction - receptors become activated

3. Response

What do you know about

1. Tight junction proteins

2. Desmosomes

3. Gap junctions

4. Hemi desosomes

5. Integrin

6. RDG

7. Fibronectin

8. Extracellular matrix

1. Tight junction proteins - seals cells together to prevent liquids like stomach acid from coming through

2. Desmosomes - welds cells together

3. Gap junctions - tunnels that allow molecules, liquids and cell signals to go back and forth between the cells

4. Hemi desmosomes - 1/2 of a desmosome

5. Integrin - proteins that integrate cell signals from the outside to the inside of the cell

6. RDG - has 3 amino acids that make up Fibronectin

7. Fibronectin - protein

8. Extracellular matrix - on the outside of the cell, if you pull the EM, you are pulling the whole cell

In G-protein receptors, when a ligand binds to the receptor, what happens to the receptor?

The receptor undergoes a change, the GDP that connects to the receptor changes into GTP

Plants and animals start life as single-celled embryos and grow through a series of cell division. What are the 2 types of cell division and how do they differ?

1. Mitosis - diploid cells (2n)

- Makes 2 identical diploid (2n) cells

- Does not make sperm and egg cells (gametes), makes every other cell (somatic cells)

2. Meiosis - diploid cells (2n)

- makes 4 haploid (1n) cells

- makes sperm and egg cells (gametes)

What are the steps of Cell division?

1. Interphase

- G1 phase

- S phase

- G2 phase

2. M phase

- Mitosis or meiosis (prophase, metaphase, anaphase, telophase)

- Cytokinesis

What happens in Prophase? (PMAT)

- The spindle apparatus made up of microtubules begins to form

- Duplicated chromosomes connect at a centromere (chromosomes condense into compact structures)

- Duplicated centrosomes are split up on the opposite sides of the nucleus

- The microtubules connect to the centromere of each chromatid pair

- nuclear membrane disassembles

What happens in Metaphase? (PMAT)

- The chromatid pairs are lined up in the middle of the cell preparing for division

- The formation of the spindle apparatus is complete

What happens in Anaphase? (PMAT)

- The centromere is cleaved (split apart)

- The newly separated chromosomes (from the chromatid pairs) are pulled apart in the direction of the centrosomes

What happens in Telophase? (PMAT)

- The chromosomes are pulled further and further apart in preparation for cytokinesis

- the nuclear membrane starts to form again

What happens in Cytokinesis?

- Actin pinches the cell to split

- Cytoplasm divides into 2 daughter cells, each have a complete set of organelles and its own nucleus

________________ consists of single long DNA double helix that is wrapped around proteins called histones

Chromosomes (made of DNA and proteins)

________________ encodes the cells genetic material

DNA

Each of the double-stranded DNA copies in a replicated chromosome are called ______________

chromatids

______________ are chromatid copies that remain attached at their centromere

Sister chromatids

______________ are the attachment site for chromatids

Centromeres

_________________ is the structure on sister chromatids where microtubules attach

Kinetochore

Where do cells spend most of their time in the cell cycle?

Interphase (cells do not divide all the time)

______________ are structures that contains a pair of centrioles

Centrosomes

What happens in the S phase of Interphase in the cell cycle?

- Chromosomes are replicated

- Centrosomes are replicated

What happens in the G1 phase of Interphase in the cell cycle?

- The first checkpoint lets the cell pass through if

a) DNA is undamaged

b) Size is adequate

c) Nutrients are sufficient

d) social signals are present

- mature cells do not pass the checkpoint, they stay in the G) state (nerve and muscle cells)

What happens in the G2 phase of Interphase in the cell cycle?

- The second checkpoint lets the cell pass through if

a) DNA is undamaged

b) Activated MPF is present

c) Chromosomes are replicated successfully

What happens in the M phase of Interphase in the cell cycle?

- The last two checkpoints let the cell pass through if

1. chromosomes are attached to the spindle apparatus

2. chromosomes are properly divided and MPF is absent

- PMAT and Cytokinesis occur

Cell cycle:

The ______________ occurs when the cells are in the process of separating their chromosomes

M phase (PMAT)

What is the difference between PMAT and cytokinesis in the M phase?

- PMAT divides the nucleus

- Cytokinesis divides the cytoplasm making new cells

______________ is the gap period between the end of M phase and the beginning of S phase

G1 phase

______________ is the gap period between the end of S phase and the beginning of M phase

G2

What happens in the G0 state and where is it located?

- mature cells that no longer need to divide stay in the G0 state (ex. nerve and muscle cells)

- located in G1

_______ phase is usually longer than the _________ phase in interphase

- G1

- G2

What is the spindle apparatus?

fibers made up of microtubules that produce mechanical forces that move replicated chromosomes

What microtubules make up the spindle aparatus?

- Polar microtubules

- Kinetochore microtubules

- Astral microtubules

Name 3 unique traits of microtubules

1. made up of alpha-tubulin and beta-tubulin dimers

2. Has a plus and minus end, making it asymmetric

3. The plus end is the site where microtubule growth normally occurs while microtubule disassembly is more frequent at the minus end

Cytokinesis:

The cytoplasm in __________ is divided by a cell plate that forms in the middle of the cell while the cytoplasm in __________ is divided by a cleavage furrow

- plants

- animals

How do Bacteria replicate?

Binary fission (does not undergo mitosis or meiosis)

True or False:

In humans, intestinal cells routinely divide twice a day to replace tissue that is lost during digestion, while mature nerve and muscle cells do not divide at all

True

True or False:

In rapidly dividing cells, G1 is eliminated

True

Defects in the control of the cell cycle can result in __________ and ___________

- cell growth

- cancer

How many checkpoints are in the cell cycle?

4

___________ is a dimer that drives immature cells into the M phase to complete their maturation

MPF (M phase promoting factor)

What two proteins make up MPF?

1. Cyclin

2. Cyclin-dependent kinase (Cdk)

___________ catalyzes the phosphorylation of other proteins to start the M phase

Cyclin-dependent kinase

__________ regulates the formation of the MPF dimer

Cyclin protein

The protein ___________ in MPF is only functional when it is bound to the cyclin subunit

Kinase (Cdk)

What happens once MPF is active?

chromosomes begin to condense, and the spindle apparatus starts to form

What happens when the cell cycle finds damaged cells?

p53 proteins either stop the cell cycle until the cell is fixed or they activate apoptosis to self-destruct the cell without damaging other cells around it

What is the difference between apoptosis and necrosis?

Cells burst when they die in necrosis, causing damage to the other cells around it while apoptosis only destroys itself without causing any harm to other cells

What happens if damaged cells make their way through the cell cycle?

Potentially cancer

In multicellular organisms, cells that keep dividing may die or form a mass of cells called a __________

Tumor

_________________ are also known as tumor suppressors

p53 proteins

What is the difference between Meiosis and Mitosis?

Meiosis

- has 2 cell divisions

- makes 4 haploid daughter cells in the gonad only

- occurs in sexual eukaryotes

- daughter cells are non-identical

Mitosis

- has 1 cell division

- makes 2 diploid daughter cells (somatic cells = autosomes)

- occurs in asexual eukaryotes

- daughter cells are identical

Each daughter cell in ___________ has the same number of chromosomes as the parent cell while each daughter cell in __________ has half the number of chromosomes as the parent cell

- Mitosis (same)

- Meiosis (half)

______________ is a cell division for growth, replacement of cells and healing wounds

Mitosis

_____________ is a cell division that produces gametes

Meiosis

What are sex chromosomes?

X and Y chromosomes (determines the sex of an individual)

What sex chromosomes are assigned to male and female individuals?

Male - XY

Female - XX

____________ are chromosomes that are not sex chromosomes

Autosomes

Chromosomes that are the same size and shape are called ________________

Homologous chromosomes

Are homologous chromosomes identical?

Not always, it depends on the alleles on each gene of each chromosome

_________ are segments of DNA that influence traits (found on chromosomes)

Genes

_____________ organisms have 2 of each type of chromosome

Diploid (2n)

______________ organisms have 1 of each type of chromosome

Haploid (n)

____________ organisms have three or more of each type of chromosome

Polyploid (3n, 4n, 5n, 6n)

What is the difference between Diploid organisms and Haploid organisms?

Diploid (2n)

- have 2 alleles of each gene

- 1 allele is carried on each of the homologs

Haploid (n)

- has 1 allele for each gene

What are these examples of?

Insects, trees, humans

Diploid organisms

What are these examples of?

Bacteria, archaea, algae, fungi

Haploid organisms

What makes up a chromosome?

- DNA

- Proteins

What is a Bivalent?

a pair of homologous chromosomes

True or False:

When 2 haploid (n) gametes fuse during fertilization, the full diploid (2n) complement of chromosomes is restored

True

Where does cell replication occur?

In interphase (S phase) before mitosis or meiosis (M phase)

What happens in Prophase I of Meiosis I?

- Spindle apparatus forms

- Nuclear membrane disassembles

- Crossing over can occur

What happens in Metaphase I of Meiosis I?

- Bivalents line up at the metaphase plate

What happens in Anaphase I of Meiosis I?

- Centromeres split up (are cleaved)

- Homologous chromosomes begin to separate

What happens in Telophase I of Meiosis I?

- Nuclear membrane reforms

- Homologous pairs separate further

- spindle apparatus disassembles

What happens in Prophase II of Meiosis II?

- Spindle apparatus reforms

- Nuclear membrane disassembles

What happens in Metaphase II of Meiosis II?

- Chromatids pairs begin to line up at the metaphase plate

What happens in Anaphase II of Meiosis II?

- Centromeres split up (are cleaved)

- Chromatids begin to separate

What happens in Telophase II of Meiosis II?

- Chromatids separate further

- Spindle apparatus disassembles

- Nuclear membrane reforms

What happens in Cytokinesis of Meiosis?

After Telophase I and II, the cytoplasm splits into two haploid daughter cells

What is crossing over?

the exchange of genetic information between homologous chromosomes

Meiosis promotes genetic variation. In what 2 ways can this be shown?

1. Crossing over (exchanging maternal and paternal alleles during Prophase I)

2. Different combinations of maternal and paternal chromosomes

True or False:

Genetic variation can occur in both sexual and asexual reproduction

False, it can only occur is sexual reproduction (Meiosis)

True or False:

Because Mitosis is the only cell division involved in asexual reproduction, asexually produced offspring are exact genetic copies of their parent

True

What are two consequences for offspring if gametes contain an abnormal set of chromosomes?

- Down syndrome

- mismarriage

_____________ occurs when an extra copy of chromosome 21 is present

Down syndrome

What is the cause of Down syndrome?

Trisomy 21

How do mistakes occur in Meiosis?

Nondisjunction

_______________ leads to gametes with abnormal chromosome numbers

Nondisjunction

Nondisjunction occurs in Meiosis I if ________________________________________________ and Meiosis II if _________________________________________________________________

Meiosis I - if homologous chromosomes fail to separate correctly

Meiosis II - if chromatids fail to separate correctly

What is the difference between Trisomy and Monosomy?

Trisomy - each cell has three copies of the same chromosome

Monosomy - there is one copy of each chromosome

Cells that have too many or too few chromosomes of a particular type are ________________

Aneuploids

Who is Gregor Mendel?

Gregor Mendel was an Australian monk that discovered genetics (how offspring inherited genes from parent cells)

Why did Gregor Mendel use garden pea plants as models in his experiments?

Garden pea plants

- Inexpensive

- easy to control

- easy and quick to grow

- produce multiple offspring

Whenever a trait appears commonly in 2 or more different forms (ex. purple and white flowers), it is called a ________________

polymorphic trait

How did Mendel control his experiments with Garden pea plants?

He performed cross fertilization

What is the difference between Mendel's single-trait and 2-trait experiments?

Single trait

- Monohybrid (crossing 2 different alleles of the same trait)

- F2 generation results in a 3:1 ratio

- 4 genotypes (4 boxes)

- 2 phenotypes

2 traits

- Dihybrid (crossing 2 monohybrids)

- F2 generation results in 9:3:3:1 ratio

- 16 genotypes (16 boxes)

- 4 phenotypes

The F1 generation is the result of the __________________ while the ______ generation is the result of the F1 generation

- parent generation

- F2

What happens to reccessive genes in F1 and F2?

Recessive genes disappear in the F1 generation and reappear in the F2 generation

_____________ are different versions of the same gene

Alleles

_______________ is the combination of alleles found in an individual

Genotype