Exam 3 - GENE 3200

Transposable elements (TE's)

_____________: general term for any genetic (DNA) unit that can reinsert elsewhere in the genome

- TE insertion can cause complete/partial loss-of-function or change of function

- Recombination can occur between linked or unlinked TEs

What are some consequence of movement of TEs into new genomic locations?

Intrachromosomal

_____________ recombination between TEs can cause chromosomal rearrangements

deletions

Intrachromosomal recombination between DIRECT repeats results in chromosomal ________________; two TEs in the same direction

inversions

Intrachromosomal recombination between INVERTED repeats results in chromosomal ________________; two TEs in the opposite direction

deletions

Interchromosomal recombination between DIRECT repeats on sister chromatids results in chromosomal _______________; two TEs in the same orientation

translocations

Interchromosomal recombination between TEs on non-homologous chromosomes results in chromosomal ___________________

Replicative, non-replicative

What are the two classes of TEs based on the mechanism of transposition?

Class I TE's

Are replicative TE's considered class I or class II?

Class II TE's

Are non-replicative TE's considered class I or class II?

Retrotransposons

What is another name for class I TE's?

DNA transposons

What is another name for class II TE's?

transposase

TE's encode _______________ that catalyzes excision and insertion

"cut-and-paste"

Nonreplicative transposition have a ____________________ mechanism (NO increase in number of copies per genome)

"copy-and-paste"

Replicative transposition have a ____________________ mechanism (increase in number of copies per genome)

1. Staggered cuts on both strands of target DNA made by transposase

2. TE joined to cut DNA

3. DNA polymerase fills in gap

Results in generation of small, flanking direct repeats at integration sites

Class I and II elements utilize similar mechanisms to insert into DNA what are they?

Barbara McClintock

____________________ was the first to propose the existence of mobile genetic elements (Detailed crosses involving a kernel pigmentation gene in maize)

Activator (Ac)

_________________ elements in maize are autonomous (intact elements that encode transposase)

Dissociation (Ds)

_________________ elements of maize are nonautonomous

A: normal levels of pigment (purple kernel).

B: No pigment synthesis (yellow kernel).

C: Normal levels of pigment (purple kernel).

What are the phenotypes of the following insertions and excisions of TE's?

Ac, Ds

In the presence of an _________ element, ________ elements can move in and out of genes

If _______ element is not present, then _______ element cannot move

________ element encodes transposase, causes _______ element to excise from original location

variegated

Transposition results in ________________ maize kernels

Cc (purple pigment)

Maize genotype is _____________

Ct; Ctc genotype (no purple pigment)

If Ds inserts into C gene it give us ________ alleles; what genotype is this?

Revertant to Cc, Purple pigment

Ds element can be excised from Ct allele, what does this do to the alleles and genotypes?

Timing of TE excision

________________ determines the size of pigmented sectors in kernel development

Early excision

_____________ results in large pigmented sectors of kernels

Late excision

____________________ results in small pigmented sectors of kernels

Class I TEs

_______________ produce a double-stranded DNA copy of the element that is then inserted elsewhere into the genome

Retrotransposons

What is another name for class I transposable elements?

long terminal repeats (LTRs)

Elements of class I TE's have ________________ at each end

reverse transcriptase (RTase)

Class I transposable elements encode ________________ that recognize the LTRs

Retroviruses

________________ have genomes composed of single-stranded RNA, carry reverse transcriptase, and infect eukaryotic cells

Retrotransposons

____________________ are 5 – 8 kb in length and integrated into eukaryotic genomes; they're also related to retroviruses

I (retrotransposons)

Majority of human TEs are class ______ (I or II) elements

Long interspersed elements (LINEs)

__________________: autonomous elements, express reverse transcriptase but lack LTRs

Short interspersed elements (SINEs)

____________________: non-autonomous elements, do not encode reverse transcriptase or any other gene products

Binary fission

_____________: simple division, separation of replicated circular prokaryotic chromosome

Chromatin

_____________: DNA and associated proteins of a chromosome

Ploidy

______________: the number of chromosome sets

Haploid (1n), Diploid (2n), Polyploid

___________: one set of chromosomes,

___________: two sets of chromosomes,

_____________: more than two sets of chromosomes

homologous pairs

Cells of sexually-reproducing organisms carry ________________ of chromosomes

Nonhomologous

_________________ chromosomes carry different genes

Sex chromosomes

____________________: unpaired X and Y chromosome

Autosomes

_______________: all chromosomes except X and Y

metaphase

The karyotype is the stained ______________ chromosomes from one cell of a normal human male

A karyotype

What is this chart called?

autosomes

Chromosomes 1 - 22 are ______________ (autosomes/sex chromosomes)

sex chromosomes

X and Y are ______________ (autosomes/sex chromosomes)

A- Submetacentric

B- Metacentric

C- Telocentric

D- Acrocentric

What are the names of these types of chromosomes?

centromere position

Types of eukaryotic chromosomes are based on __________________

centromere, telomeres

Each eukaryotic chromosome has a __________ and two __________

A- Telomere

B- Centromere

C- Kinetochore

What are these labels showing?

M-phase & interphase

What are the 2 major phases of the eukaryotic cell cycle?

M-phase= mitosis and cytokinesis

Interphase= cell growth & function

What happens during M-phase? What about Interphase?

A: G1 phase, B: S-phase, C: G2 phase

What are the 3 subphases of interphase?

Stable, non-dividing period

What happens during G0 phase?

Growth and development of the cell

What happens during G1 phase?

Synthesis of DNA

What happens during S phase?

Preparation for division

What happens during G2 phase?

M-Phase: 1 hr, Interphase: 23 hrs

About how long is M phase? Interphase?

10 hrs, 9 hrs, 4 hrs

About how long is G1 phase? S-phase? G2-phase?

Sister chromatids

________________: identical copies of each chromosome present after each S-phase and held together at their centromeres

Sister centromeres

Centromeres of sister chromatids are ________________

unlinked

The A and B genes are _____________

alleles

A and a are _________ of the A gene.

B and b are _________ of the B gene.

A- Sister chromatids,

B- Nonhomologous chromosomes

C- Nonsister chromatids

What is the following picture labeling?

G0

_____________ phase: terminal differentiation and arrest of cell division (stable non-dividing period)

A: G1=4, S=4, G2=4, Pro=4, Met=4, Ana=8, Tel=4

B: G1=4, S=4-8, G2=8, Pro=8, Met=8, Ana=8, Tel=4

C: G1=6, S=6-12, G2=12, Pro=12, Met=12, Ana=12, Tel=6

Fill in the chart

Spindle apparatus

What is responsible for chromosome movement and segregation?

microtubule

The spindle apparatus is a _________-based structure

Tubulin

Microtubules are made of what?

Centrosome

______________: Microtubule organizing center

Centrioles

______________: Pair of small, darkly stained bodies at center of centrosome

Kinetochore

Multi-protein complex at the centromere of each chromosome & Attachment site for spindle fibers

The ________________ attaches to the centromeres

Interphase, Prophase, Prometaphase, Metaphase, Anaphase, & Telophase

Mitosis is divided into 6 stages, what are they?

The cell grows and makes copies of its DNA

What are the major events that occur in interphase?

The nucleolus disappears and chromosomes condense and become visible

What are the major events that occur in prophase?

Nuclear envelope breaks down, kinetochores appear at the centromeres and mitotic spindle microtubules attach to kinetochores

What are the major events that occur in prometaphase?

Chromosomes are lined up and each sister chromatid is attached to a spindle fiber

What are the major events that occur in metaphase?

Each of the sister chromatids are pulled to opposite ends of the cell

What are the major events that occur in anaphase?

Chromosomes arrive at opposite poles, and nuclear envelope material surrounds each set of chromosomes

What are the major events that occur in telophase?

Checks to see if the cell has all the enzymes and proteins needed for S phase

What happens during G1/S checkpoint

Checks to see if the DNA is replicated and undamaged

What happens during G2/M checkpoint

Checks to see if each chromosome is aligned on the metaphase plate and attached to spindle fibers from opposite centrosomes

What happens during spindle assembly checkpoint (SAC)?

Mitosis goes through one round and gives 2 daughter cells that are genetically identical. Meiosis goes through 2 rounds and results in 4 daughter cells that are not genetically identical

What is a key difference between mitosis and meiosis?

-Meiosis I: reductional division

-Meiosis II: equational division

What is another name for meiosis I? What about meiosis II?

Synapsis of homologous chromosomes, recombination, & separation of homologous chromosomes

What happens during meiosis I?

Separation of sister chromatids

What happens during meiosis II?

Chromosomes condense, each chromosomes possesses 2 chromatids, & the mitotic spindle forms

What happens during the middle of prophase I?

The nuclear membrane disintegrates, & spindle microtubules attach to chromatids

What happens during late prophase I?

Homologous chromosomes line up on the metaphase plate and the spindle fibers attach to the homologs

What happens during metaphase I?

Homologous chromosomes are pulled to opposite sides of the cell and some recombinant chromatids can occur

What happens during anaphase I?

Chromosomes arrive at spindle poles, the nuclear membrane reforms, & the chromosomes relax

What happens during telophase I?

A new spindle forms around the chromosomes, & sister chromatids condense. Later in the phase the nuclear membrane disintegrates, & spindle microtubules attach to kinetochores on the sister chromatids

What happens during prophase II?

Sister chromatids line up on the metaphase plate and the spindle fibers attach

What happens during metaphase II?

Sister chromatids are pulled to opposite ends of the cell

What happens during anaphase II?

Chromatids arrive at spindle poles, the nuclear membrane reforms and cleavage furrows divide the 2 cells into 4

What happens during telophase II?

Chromosomes have 4 legs and chromatids have 2

What is the difference between chromosomes and chromatids?

synapsis, recombine

Homologs enter ______________, _____________, and then segregate