MSSTATE PLANT BIOLOGY 2113 TEST 4

Sexual Reproduction (2 parents)

• Creates genetically different offspring

• Unstable environment

• Some offspring are more adapted than their parents, some offspring are less adapted than their parents

Asexual Reproduction (1 parent)

• Creates genetically identical offrspring

• reproduce in isolation (1 parent)

• Stable environment

• Same level of adaptation as parent

EX: strawberry

What form of nuclear division is associated with asexual reproduction?

mitosis

What form of nuclear division is associated with sexual reproduction?

meiosis

Meiosis

sexual reproduction

• 2 haploid gametes combine to form a Diploid zygote (new organism)

haploid

1 set of chromosomes

diploid

2 sets of chromosomes

What is the goal of meisosis 1?

separate homologous chromosomes

What is the goal of meiosis 2?

separate sister chromatides

What are the steps of meiosis 1?

1. Prophase I

2. Metaphase I

3. Anaphase I

4. Telophase I

5. Cytokinesis

Prophase I (basic def) - MEIOSIS I

• nucleolus breaks down

• starts forming spindle

• nuclear envelope breaks down

• DNA condenses

Prophase I (IN DEPTH) - MEISOSIS I

•Leptotene -> DNA condenses

•Zygotene -> pairs of chromatids find each other and pair up - synapse (known as homologous chromosomes)

•pachytene -> crossing over occurs

• Diplotene -> homologous chromosomes begin moving away from each other

• Diakinesis -> homologous chromosomes continue moving away from each other and remain connected by the centromere

Metaphase I - MEIOSIS I

• homologous chromosomes line up in the middle of the cell.

Anaphase I - MEIOSIS I

• Homologous chromosomes are pulled apart to opposite ends of the cell.

Telophase I - MEIOSIS I

• nuclear envelope reforms

• nucleoli reforms

• spindle breaks down

• DNA begins unraveling

Cytokinesis - MEIOSIS I / MEIOSIS II

• division of the cytoplasm

• either follows telophase I and telophase II to produce 4 haploid cells

• or occurs twice after telophase II, still produces 4 haploid cells

What are the steps to meiosis II?

1. Prophase II

2. Metaphase II

3. Anaphase II

4. Telophase II

5. Cytokinesis

Prophase II

• nucleolus breaks down

• starts forming spindle

• nuclear envelope breaks down

• DNA condenses

Metaphase II

• chromatids line up in the middle of the cell

Anaphase II

• chromatids separate and move to opposite ends of the cell.

• Chromatids are now called chromasomes

Telophase II

• nuclear envelope reforms

• nucleoli reforms

• spindle breaks down

• DNA begins unraveling

Does cytokinesis typically occur to produce egg cells?

No, four haploid nuclei are in a single cell, and three of them break down, and the one remaining absorbs the nutrients and becomes the egg cell

Alternation of generations

The complex life cycle of plants. (sexual reproduction in agiosperms)

TWO TYPES

1. sporophyte generation

2. gametophy generation

Sporophyte generation

• diploid

• produces haploid spores through meiosis

EX:

mircrospores (male)

megospores (female)

Gametophyte generation

• haploid, develops from haploid spores that undergo mitosis

• produces gametes that can fuse to form a diploid zygote and eventually a diploid sporophyte

EX:

microgametophyte -> pollen grain (male)

megagametopphyte -> emoryosack (female)

What are the 4 main flower parts?

1. sepal

2. petal

3. stamen

4. carpel

sepal

encloses flower bud

petal

colorful fragranr leaves to attract pollenators

stamen

"male" part of the flower, composed of anther and a filament

carpel

"female" parts of flower composed of stigma, style, and ovary

What are flowers called if they have all 4 parts?

complete flower

What are flowers called if they do not have all 4 parts?

incomplete flowers

stigma

sticky area where pollen lands

pollination

process of pollen grain landing on stigma

cross pollination

pollen from a seperate individual plant lands on the stigma of another plant

self pollination

pollen from a single flower on an individual plant or pollen from a different flower on the same plant lands on the stigma.

style

upholds the stigma, connects stigma to ovary

ovary

place where megaspores are made

placente

area of tissue in ovary where ovules are attached

micropyle

opening in the ovule where integuments (thin layers of cells) are not present, important for the entry of the pollen tube

what happens to ovule after successful fertilization?

ovule becomes a seed.

what happens to the ovary after successful fertilization?

ovary becomes the fruit

What is an example of an ovary with 1 ovule after successful fertilization?

a peach with 1 large seed in the fruit

What is an example of an ovary with many ovules after successful fertilization?

a tomato that has many seeds

What do haploid microspores develope into?

microgametophytes (male) = pollen grain

What do microgametophytes produce?

A vegetable cell and a generative cell (2 sperm cells)

Why is the vegetable cell important?

Important for pollen tube formation

What happens when the pollen grain lands on the stigma?

• produces a pollem tube that travels down style and to the ovary

• the pollen tube contains the two sperm cells

What is another name for a female gametophyte?

megagametophyte (embryosac)

What happens to the 1 remaining megaspore?

Developes into the megagametophyte (embryosac)

What are the stages of the 3 divisions in female gametophytes?

Begin with 1 haploid nucleus inside large cell

1. Mitosis division 1 - produces 2 haploid nuclei

2. Mitosis division 2 - produces 4 haploid nuclei

3. Mitosis division 3 - produces 8 haploid nuclei

What is the result of the deposition of the cell wall components?

7 separate cells but 8 nuclei

• egg cell (1)

• synergies (2)

• antipodals (3)

• polar nuclei (2) -> in one large cell

plasmogamy

the gametes protoplast join together

protoplast

The contents of a plant cell exclusive of the cell wall.

karyogamy

the gametes nuclei join together

What are the stages of fertilization?

• pollentubes is directed to the ovules

• enters a synergid (ground crew)

• the tube of the pollen tube burst and releases two sperm cells

• 1 sperm cell fuses with egg cell (zygote), and other sperm cell fuses with two polar nuclei to form triploid endosperm. This process is called double fertilization.

What plant species is double fertilization unique to?

Angiosperms

What is the triploid endosperm used for?

provides nutrition for the zygote and later on in the line nutrients for the embryo.

By which process does the zygote (later on embryo) divide by?

Mitosis

Differential gene activation

All the cells of an organism have the same genome, but expression of genes differs as cells differentiate.

DNA

• Blueprint for life, instructions to make proteins.

• long term storage of genetic information, stays in nucleus

• components = deoxyribose, nitrogen base, phosphate

What is DNA wrapped around to make it fit inside the nucleus?

Histone proteins (DNA + histones = nucleosome)

Gene

portion of DNA that encodes amino acid squence

genetic code

20 different amino acids to make proteins

Codon

nucleotides of mRNA read as a sequence of 3, 64 possible codons, nearly universal across life.

What is the codon for that encodes for the start protein methionine?

AUG

What are the stop codons?

UAA, UAG, UGA

Structural region

codes for amino acid sequence

promotor

directs synthesis of mRNA from the structural regian toward the 5` end of the structural region (upstream()

TATA Box

Site where RNA polymerase II binds to

Enhancer element

DNA sequence upstream/toward the 5` end that increases ability of polymerase II to transcribe a gene

Exons

DNA sequences that will be expressed as amino acid sequences.

Introns

sequences that wont be expressed

Transcription

• Synthesis of RNA from a DNA strand

What does transcription start with?

• RNA polymerase II across a start signal on DNA.

• After this occurs, the two strands of DNA separate over a small area, then, ribonucleotides diffuse to the area.

Where are hydrogen bonds found?

Between nitrogen bases of DNA template strand, and growing RNA strand.

A-U

G-C

How long does transcription occur for?

Process continues indefinitely umtil a stop signal is reached on DNA strand.

What is produced from transcription?

Heterogeneous nuclear RNA

What modifications are done to the RNA produced from transcription?

• introns are removed

• poly A tail is added (200 adenines) to the 3` end

• 7 methyl guanosine cap is added to the 5` end.

What happens to the mRNA after the modifications are performed?

mRNA can now be exported from the nucleus.

Translation

• reading of mRNA by ribosomes to make proteins

• involves ribosomes and tRNA.

What are the 3 steps of translation>

1. initiation

2. elongation

3. termination

Ribosomes

• read mRNA coons

• two subunits (small and large)

• each made of a protein and a ribosomal RNA (rRNA)

• has a grove to hold mRNA strand

What are the 3 sites formed when small and large come together?

E (exit site)

P (peptidyl site)

A (aminoacyl site)

tRNA

• Carries amino acids to the ribosome

• carry anticodons complementary to codons on mRNA

• reads from 5` to 3`

what is the first stage of translation?

initiation

what are the steps of initiation?

• Involves mRNA, initiator tRNA, ribosomal subunits, and initiation factors

• Recognition of the 7-methyl guanosino cap at the 5' end of the mRNA

• Binding of mRNA to the small ribosomal subunit

• The initiator tRNA, which carries methionine, recognizes the start codon (AUG) and binds

• To end initiation, the large ribosomal subunit joins with the small ribosomal subunit

What promotes binding of the mRNA strand to the small ribosomal subunit?

recognition of the 7-methyl guanosine cap at the 5` end of the mRNA

where is the initiator tRNA located?

In the p-site (peptidal site)

What is the second stage of translation?

elongation

Elongation

Involves a covalent bonding of amino acids individually to produce a polypeptide.

How does elongation occur?

• Charged tRNA binds to the A site because the anticodon and codon are complementary.

• a peptide bond is formed between the amino acid in the A site and the growing polypeptide.

• this results in a polypitidy transfer reaction to occur

• As a result the ribosome shifts towards the 3` end by one codon, which shifts the tRNA in the p-site to the E-site.

• Then the tRNA in the A-site shifts to the p-site allowing for the next charged tRNA to be able to enter the a-site

peptidyl transfer reaction

Occurs when a polypeptide is removed from tRNA in the p-site to tRNA in the A-site.

How many ribosomes can translate the same mRNA strand at once?

Multiple ribosomes can translate the same mRNA strand at once to form a polysome.

What is the third stage of translation?

Termination

Termination

• Elongation ends when a stop codon reaches the A-site of a ribosome.

• UAA, UAG, UGA, are recognized by a release factor.

• The polypeptide is attached to the tRNA in the p-site

• the polypeptide and tRNA are released separately from ribosome.

• mRNA, two ribosomal subunits, and the release factor separate.

How is the bond between tRNA in the p-site and the polypeptide broken?

With water through the process of hydolysis.

genetics

branch of science about inheritance.

alleles

forms of genes

genotype

alleles of an organism