Bio exam 3 meiosis and mitosis

trait

• any distinct, observable, or measurable characteristic of a living organism

• part of phenotype

• controlled by DNA

DNA

• Deoxyribose nucleic acid is built by attaching the phosphate of one nucleotide to the sugar of the next

• 2 linear strands of nucleotides

• A nucleotide is made up of nitrogenous base, sugar, and a phosphate

• 4 types of nucleotide

  • Adenine

  • Cytosine

  • Gunaine

  • Thymine

complementary base pairing

• A and T

• G and C

gene

• Sequence of nucleotides that code for proteins

• Located on chromosomes

DNA of prokaryote

• DNA is a circular loop, no start or end

• single circular chromosome attached to the cell membrane with binding proteins, no nucleus

DNA of eukaryote

• most of there DNA doesnt code for proteins!

• Contain linear chromosomes wrapped around histones (forming chromatin) within a nucleus

genome

• The complete set of all chromosomes / DNA in a cell

• All cells within an organism have the same genome

alleles

• Different versions of a gene that code for the same trait

• Ex = blue eyes or brown eyes

intron

Non coding DNA within a gene

exon

• The parts of the gene that code for proteins

RNA splicing

• Some genes can code for multiple types of proteins

  • Different combinations of exons can be included or excluded to produce multiple types of proteins from one gene

chromatin vs chromsome

When a cell is not dividing, DNA exists as loose, uncoiled chromatin. When the cell prepares to divide, this chromatin condenses into distinct, tightly packed chromosomes

where are proteins made

outside of the nucleus in the rough ER

nuclear pores

openings in the nucleus that let mRNA leave and go into cytoplasm

ribosomes role in transcription and then translation

pick up the mRNA once it leaves the nucleus and carry it to rough ER, then it turns to translation process once it gets to rough ER

RNA polymerase in transcription

• Makes a polymer of RNA

• It scans a gene and separates the 2 strands of DNA

• It then matches RNA nucleotides with the complementary DNA nucleotides

• This builds mRNA 

• only template strand of DNA is copied to RNA

promotors in transcription

• Special DNA sequence that acts as a landing spot for RNA polymerase 

• Located upstream of the gene

  • Like the airport guys with the glow up vests and wands telling ur airplane where to land in the dark

terminators in transcription

• A special DNA sequence that tells RNA polymerase to stop

• Located downstream of the gene

coding sequence in transcription

• Codes for the actual protein

• The only thing transcribed to mRNA

RNA

• ribonucleic acid

• has uracil instead of thymine

• single strand

what organelle performs translation

ribosomes, they have 2 sub units that form a sandwich around the mRNA

codon

set of 3 nucletodies

peptide bond

links amino acids

basic run down of translation

1. Ribosomes carry the mRNA to the rough ER to begin making the protein

2. Ribosome reads the mRNA codons

3. It then links the codons with the corresponding anticodon of tRNAs

4. The amino acids on the tRNAs are linked together via peptide bonds in the specific order specified by the codons

5. Polypeptide (protein) formed!

tRNA aka transfer RNA

• its a highly folded RNA strand that makes a T shape

• one end has anticodon that matches to the mRNA codon (complementary)

• the other end is an amino group

• Each tRNA has a unique anti codon and a unique amino acid

anticodon

part of tRNA that is complementary abnd matches to mRNA codon

AUG codon

• means start

• corresponds to MET (amino acid called methyonine)

• all proteins need to start with MET

UGA, UAA, UAG codons

stop

gene expression

• The process of producing a protein encoded by a gene

• Turning on and off genes

• Explains how we can have different cell types despite almost all cells in our body having the same DNA and genes

transcription factors

• Bind directly to special DNA sequences near the promoters of the genes they regulate, specific for one gene

• Different cell types have different combinations of these transcription factors to turn genes on and off, depending on the function of the cell

• TYPES = activators and repressors

activators in transcription

•  transcription factors that recruit RNA polymerase to transcribe a gene 

repressors in transcription

•  transcription factors that block RNA polymerases’s access to the promoter, repressing gene expression

epigenetics (histone modifications)

• Includes any factors that alter chromatin structure w/out changing DNA sequence

• Histones can be modified by adding chemical groups to the tails (dangling amino acid chains)

• depending on what chemical group is added to the histone tails, the histones can move closer together or further apart

what happens when histones move closer together (epigenetics)

• results in inaccessible DNA and an inactive gene in compact DNA

what happens when histones move further apart (epigenetics)

• active genes in non compacted DNA (spaced out histones) are accessible for transcription

mutations

• Changes to DNA sequence can result in mutation

• Some mutations in genes result in changes to the protein they code for 

• Some mutations can cause disease

point mutations

• Single nucleotide change

• 3 types of point mutation:

  • Substitutions 

  • Insertions

  • Deletions

substitution point mutation

• one nucleotide is changed for another

• The protein can still function, especially if the amino acid is in the same group

insertion point mutation

• add a nucleotide

• causes a frameshift in which all codons after the mutation are altered

• Protein is extremely mutated and no functional

deletion point mutation

• remove a nucleotide

• causes a frameshift in which all codons after the mutation are altered

• Protein is extremely mutated and no functional

chromosomal abberation

• Entire sections of chromosome are altered

  • Deletion of gene

  • Relocation of gene

  • Duplication of gene

how do mutations happen

• Spontaneous mutations

  • Accidents during DNA replication

  • DNA repair enzymes correct most errors but not all

• Radiation induced mutations

  • X rays or sunlight can disrupt atomic structure

• Chemical induced mutations

  • Chemicals like vape or cigs react w atoms in our DNA molecules and cause mutation

telomeres

• protective caps of non-coding DNA at the tips of every chromosome that prevent the loss of protein-coding DNA

• Telomeres get shorter after each cell division

• when all gone it results in cell death

primary factors in aging

Shortening telomeres and the eventual death of stem cells

asexual repro

• mitosis of unicellular organisms

• binary fission= one cell divided and produces a whole new organism

meiosis

• Division of germ line stem cells to produce gametes

mitosis

division of somatic cells, takes 24 hours

interphase

• for growth and preparation before mitosis

• consists of G1, s phase, and G2

G1

• Primary growth phase

• normal cellular functions take place

• Some cells pause here and enter a resting state called G0 for days or years

S phase - aka DNA synthesis

• The cell makes preparations for division by creating an exact duplicate of every chromosome (replication)

G2

• Second period of growth and preparation for cell division

2 phases of human cell division

stage 1 = interphase

stage 2 = mitotic phase

mitotic phase of human cell division

has mitosis and cytokinesis

cancer

uncontrolled and rapid cell division

diploid

• having 2 copies of each chromosome

homologous chromosomes

• the two copies of each chromosome type

fertilization

•  fusion of egg and sperm

  • In humans, each parent donates one copy of each chromosome

haploid

• only have one copy of each chromosome

gamete

• egg and sperm cells

  • Have 23 chromosomes

end result of mitosis

2 genetically identical diploid cells

end result of meiosis

4 haploid gametes

TOTAL # chromosomes in non sex cell

46

3 phases of meiosis

1. DNA replication

2. meiosis 1

3. meiosis 2

Goal of Meosis 1

• The goal is to separate the replicated homologous chromosomes are separated into two cells

Goal of meiosis 2

• Sister chromatids seperate

sexual repro

• fusion of 2 cells, one from each parent

nondisjunction

•  inability for homologous chromosomes to separate in meiosis 1

  • You get gametes with incorrect number of chromosomes

  • Trisomy 21 = extra copy of chromosome 21, downsyndrome

genetic changes in somatic cells, can they be passed down?

no

how is zygote formed

haploid gametes produced via meiosis fuse together to form a single celled zygote

• The zygote is diploid, containing two copies of each chromosome (one from mom and

one from dad)

• The zygote starts to divide like crazy due to mitosis , and all of our cells in our body come from this zygote

meiosis 1

• S phase 

  • Dna replication

• Prophase 1 

  • Replicated chromosomes condense

  • Nuclear membrane degrades

  • Mitotic spindle made

  • SYNAPSIS and CROSSING OVER (MAJOR DIFFERENCE FROM MITOSIS)

    • Synapsis lines the replicated homologous chromosomes up

    • During crossing over the sister chromatids of the homologous chromosomes swap regions of DNA

• Metaphase 1

  • The replicated homologous chromosomes are aligned in center of cell

• Anaphase 1 

  • Homologous chromosomes pulled apart

  • Different from MITOSIS where sister chromatids were pulled apart

• Telophase 1 and cytokinesis

  • 2 diploid cells made, each contain a mix of replicated homologous chromosomes, they are genetically different then the parent

meiosis 2

• No s phase like in meiosis 1

• Same thing happens except its with sister chromatids

• 4 genetically different haploid cells, they have 1 copy of each chromosome type and then either an X or a Y

• Due to crossing over, that one copy of each chromosome they have has a mixture of DNA from dad and mom (both homologous chromosomes