College Bio Test 3 (ch 10-13)

Jefferson Academy Concurrent Enrollment

What is a zygote?

Fertilized egg/embryo

What is a genome?

A cell’s DNA

What is a nucleoid?

Prokaryotic region housing DNA

What is a plasmid?

Mini non-essential DNA loops

What is a gamete?

Sex cell

What is a somatic cell?

Typical body cell

What does diploid mean?

2n, two matched sets of chromosomes

What is a haploid?

1n, one set of chromosomes

What is a homologous chromosome?

Matched pair of chromosomes

What is a gene?

Functional unit of chromosomes

What is a trait?

Variations of characteristics coded by genes

What are histone proteins?

Proteins for DNA strands to wrap around

What is chromatin?

Noodles of DNA and histone proteins

What is a nucleosome?

DNA strand wrapped around many histones like beads on a string

What is a sister chromatid?

Identical parts of a replicated chromosome attached at a centromere

What is a centromere?

Connection between sister chromatids

What happens in the G1 phase?

1. Accumulates DNA building blocks

2. Accumulates DNA-associated proteins

3. Accumulates sufficient energy to replicate chromosomes

What happens in the S phase?

1. Chromosomes are synthesized into sister chromatids

2. Mitotic spindle and centrioles appear

What are centrioles?

Organizing center for mitotic spindle

What happens in G2?

1. Energy replenished

2. Proteins necessary for chromosome manipulation synthesized

3. Duplicated organelles

4. Cytoskeleton dismantled

5. Growth

What happens in Prophase (mitosis)?

1. Chromosomes condense

2. Spindle fibers emerge from centrosomes

3. Nuclear envelope breaks down

4. Nucleolus disappears

What happens in Metaphase (mitosis)?

1. Mitotic spindle is fully developed

2. Chromosomes line up in the center

3. Sister chromatids attached to mitotic spindle

What happens in Anaphase (mitosis)?

1. Sister chromatids unbound to each other

2. Sister chromatids pulled to opposite sides (now they’re chromosomes!)

3. Cell elongates

What happens in Cytokinesis (mitosis)?

1. Animal cells: cleavage furrow separates daughter cells

2. Plant cells: cell plate emerges

What is G0?

Cells not actively preparing to divide where cells exit the cell cycle

What does the G1 checkpoint do?

Determines if all conditions are favorable for cell division:

1. Adequate energy and material reserves

2. Correct size

3. DNA damage check

What does the G2 checkpoint do?

Bars entry into the mitotic phase if conditions are not met:

1. Adequate size

2. Protein reserves are high

3. Chromosomes are all replicated

4. Replicated DNA is not damaged

What does the M Checkpoint do?

Determines if all of the sister chromatids are attached to the spindle correctly

What is positive regulation?

regulation that promotes mitotic progress

What is negative regulation?

regulation that halts the cell cycle

What are cdk/cyclin complexes?

cyclin proteins + cyclin-dependent kinases (cdks) that are phosphorylated and advance cells to the next stage

What is p53?

regulatory protein that halts the cell cycle if DNA is damaged during G1

1. recruits enzymes to fix the DNA

2. or commits apoptosis

What is p21?

regulatory protein that inhibits cdk/cyclin complexes when p53 says so

What is retinoblastoma protein (Rb)?

regulatory protein that blocks transcription factors (like E2F) which halt stage progression

What is a proto-oncogene?

genes that code for positive cell cycle regulators

What is an oncogene?

mutated gene that cause cells to become cancerous

What is a tumor-suppressor gene?

Segments of DNA that code for negative regulator proteins

What is binary fission?

Prokaryotic cell division

What is Chargaff’s rule?

A=T, C=G

What does antiparallel mean?

3’ end of one strand faces the 5’ end of the other

What are the building blocks of DNA?

nucleotides (deoxyribose, nitrogenous base) and phosphate groups

Which bases are purines?

A, G, they have a double ring structure

Which bases are the pyrimidines?

C, T, have a single ring structure

What is supercoiling?

Prokaryotic DNA packing

What is the conservative replication model?

two parent DNA strands stay together, two daughter strands stay together

What is the dispersive replication model?

Each daughter DNA strand has a mix of parent and new sequences

What is the semi-conservative replication model?

Each daughter DNA molecule has one parent strand and one new strand, this is the correct model

How does DNA replicate in prokaryotes?

Starts in an origin on a circle and works in both directions to the opposite side of the circle

What is the origin of replication?

Place where DNA strands are split apart

What is helicase?

Enzyme that unwinds DNA

What is a replication bubble?

Space of unwound DNA

What is a replication fork?

Y shaped ends of replication bubble

What is topoisomerase?

Enzyme that prevents DNA from being wound too tightly

What are single-strand binding proteins?

Proteins that prevent the DNA from winding back into a double-helix during replication

What are the limitations on DNA polymerase III?

1. Needs a free 3’- hydroxyl group (RNA primase provides a primer for DNApol3 to add on to)

2. Can only synthesize in the 5’ to 3’ direction

What is the leading strand?

Strand going 5’ to 3’ that can be synthesized with one primer

What is the lagging strand?

Strand going 3’ to 5’ that is synthesized with multiple primers in Okazaki fragments

What are the steps of DNA replication?

DNA Unwinds

1. Helicase unwinds the DNA

2. Single Strand binding proteins prevent DNA from rewinding

3. Topoisomerase prevents supercoiling

   Replication

4. Primase synthesizes RNA primers for each parent DNA strand

5. DNApol3 adds nucletides to 3’-OH end of each primer to create leading strands

6. Primase adds more primers to lagging strands

7. DNApol3 extends lagging strand

8. Okazaki fragments synthesized

9. DNApol1 removes RNA primers and replaces with DNA

10. Ligase joins Okazaki fragments

What is a telomere?

End of a chromosome made of 100-1000 TTAGGG sequences

Why do lagging strand telomeres shrink?

Primers don’t fit anymore and that region of the chromosome can’t be replicated any more

What does telomerase do?

replicates telomeres to prevent their shortening in germ cells and adult stem cells

What is proofreading?

DNApol catches mistakes and corrects wrong bases

What is mismatch repair?

Incorrect bases swapped

What is nucleotide excision repair?

Sections of DNA removed and replaced with the correct version

What is a mutation?

Variation in the nucleotide sequence of a genome

What is sexual reproduction?

Fertilization of gametes from two parents

What is meiosis?

Creation of gametes

What is a spore?

haploid cells that can produce a haploid organism OR fuse with another spore into a diploid organism

What happens in Prophase I (meiosis I)?

1. Homologous proteins attach to each other in synapsis held together by synaptonemal complex

2. Segments of homologous chromosomes cross over and trade information

What is crossing over?

first source of genetic variation

swapping the same gene from maternal and paternal homologs

What happens in metaphase I (meiosis I)?

homologous chromosomes line up in the center in random arrangement (2nd form of genetic variation)

What happens in Anaphase I (meiosis I)?

microtubules pull homologous chromosomes apart (sisters still bound!!!)

What happens in Telophase i (Meiosis I)?

separated chromosomes arrive at opposite poles and split into 2 cells

What happens in Prophase II (meiosis II)?

Sister chromatids attach to microtubules from opposite poles

What happens in Metaphase II (meiosis II)?

sister chromatids are condensed and align in the center

What happens in Anaphase II (meiosis II)?

sister chromatids pulled apart

What happens in Telophase II (meiosis II)?

1. chromosomes on opposite sides and decondense

2. nuclear envelope forms

3. cells split into 4 genetically different cells

Differences between Meiosis and Mitosis

Mitosis:

1. singular nuclear division

2. results in 2 identical cells

Meiosis:

1. double nuclear division

2. four haploid different cells

3. meiosis I is reduction division (2n to 1n)

What is a karyotype?

number and appearance of chromosomes

What is nondisjunction?

Improper splitting of homologous chromosomes or sister chromatids in meiosis I or II

What is euploidy?

Normal amount of chromosomes

What is aneuploidy?

Abnormal amount of chromosomes

What is monosomy?

Missing a chromosome (ex. only one version of chromosome 1).

What is trisomy?

extra chromosome (ex. 3 copies of chromosome 21)

What chromosomes can be trisomic and result in a surviving organism?

13, 15, 18, 21, 22

What is polyploid?

Extra chromosome sets (ex. diploid egg + haploid sperm)

What is X inactivation?

One X in females is inactivated because they only need 1 to live

What is a Barr body?

inactivated X chromosome in females

What is a diploid dominant organism?

The only haploid cells are gametes

What is a haploid-dominant organism?

zygotes formed in sexual reproduction turn into four haploid cells (spores) through meiosis instead of 1 individual

What is continuous variation/quantitative variation?

Many genes work together to determine a characteristic

What is discontinuous variation/qualitative variation?

Discrete traits that do not depend on others

What does true-breeding mean?

Self-fertilized organisms only have offspring that resemble themselves

What is a hybridization?

Manipulation of traits

What is the P/F1/F2 generation?

P = parent

F1 = first filial

F2 = second filial

What is the principle of segregation?

Individuals have two copies of each trait and each parent transmits one copy to its offspring

What is the Chromosomal Theory of Inheritance?

Genetic factors are carried on chromosomes which are passed to offspring

What is an allele?

Different versions of genes

What is homozygous?

two identical alleles

What is heterozygous?

two different alleles