Exam 1 Book Notes

somatic cells

cells in an organism other than gametes and their precursors

somatic cells

make up most of each organism’s tissue throughout the lifetime of the individual

germ cells

specialized cells that undergo meiosis

germ cells

cells that transmit genes to the next generation

meiosis 1

parent nucleus divides to form 2 daughter nuclei

meiosis 1

starts with the duplication of chromosomes

prophase 1 leptotene

chromosomes begin to condense

prophase 1 leptotene

centrosomes begin to move toward opposite poles

prophase 1 zygotene

homologous chromosomes enter synapsis

prophase 1 zygotene

the synaptonemal complex forms

prophase 1 pachytene

synapsis is complete

prophase 1 pachytene

crossing over happens

crossing over

genetic information exchange between non sister chromatids of a homologous pair

prophase 1 diplotene

synaptonemal complex dissolves

prophase 1 diplotene

a tetrad of 4 chromatids is visible

prophase 1 diplotene

crossover points appear as chiamata

prophase 1 diplotene

meiotic arrest occurs at this time in many species

prophase 1 diakinesis

chromatids thicken and shorten

prophase 1 diakinesis

the nuclear membrane breaks down

prophase 1 diakinesis

spindle begins to form

metaphase 1

tetrads line up along the metaphase plate

metaphase 1

each chromosome of a homologous pair attaches to fibers from opposite poles

metaphase 1

sister chromatids attach to fibers from the same pole

anaphase 1

sister centromeres remain connected to each other

anaphase 1

the chiasmata dissolve

anaphase 1

homologous chromosomes move to opposite poles

telophase 1

the nuclear envelope re-forms

telophase 1

resultant cells have half the number of chromosomes

• each consisting of 2 sister chromatids

telophase 1

cytokinesis separates the 2 daughter cells

interkinesis

similar to interphase

• no chromosomal duplication takes place

interkinesis

chromosomes decondense

recombination

the process where offspring derive a combination of alleles different from the parent creating the new generation new allelic combinations of genes which makes the sister chromatids no longer identical

prophase 2

chromosomes condense

prophase 2

centrioles move toward the poles

prophase 2

nuclear envelope breaks down at the end

metaphase 2

chromosomes align at the metaphase plate

metaphase 2

sister chromatids attach to spindle fibers from opposite poles

anaphase 2

sister centromeres detach from each other

• allows sister chromatids to move to opposite poles

telophase 2

chromosomes begin to uncoil

telophase 2

nucleo envelopes and nucleoli re-form

cytokinesis

cytoplasm divides

• forms 4 new haploid cells

synapsis

process where homologous chromosomes become aligned and zipped together

synaptonemal complex

structure that helps align homologous chromosomes

bivalent

a pair of synapsed homologous chromosomes

tetrad

4 synapsed homologous chromsomes

equational division

cell division that does not reduce the number of chromosomes, but distributes sister chromatids to the 2 daughter cells

nondisjunction

the homologs of a chromosome pair don’t segregate during meiosis 1

mitosis

in all eukaryotic cells

mitosis

when followed by cytokinesis it increases the number of cells

mitosis

happens in somatic cells and germ-line precursor cells

mitosis

in haploid and diploid cells

mitosis

one round of division

mitosis

after the S phase

mitosis

homologous chromosomes don’t pair

mitosis

genetic exchange between homologous chromosomes is rare

mitosis

sister chromatids attach to spindle fibers from opposite poles during metaphase

mitosis

centromeres of the sister chromatids separate at the beginning of anaphase

mitosis

produces 2 new daughter cells

• they are identical to each other and the original cell

mitosis

is genetically conservative

meiosis

only in sexually reproducing organisms

meiosis

in germ cells

• because its part of sexual cycle

meiosis

has 2 rounds of division

meiosis

only in diploid cells

meiosis

chromosomes duplicate before meiosis 1 but not before meiosis 2

meiosis

homologous chromosomes pair along their length during prophase

meiosis

crossing over between homologous chromosomes during prophase

meiosis

homologous chromosomes attach to spindle fibers from opposite poles

meiosis

centromeres of sister chromatids stay tightly attached to

meiosis

sister chromatids attach to spindle fibers from opposite poles

meiosis

centromeres of sister chromatids separate at beginning of anaphase

meiosis

produces 4 haploid cells

• 1 egg or all sperm (all can become gametes

• non are identical

transformation

the ability of a substance to change the genetic characteristics of an organism

transcription

protein reading information in a single DNA strand by synthesizing a stretch of RNA

wild-type alleles

the allele found on the large majority of chromosomes in the population under consideration

forward mutation

a mutation that changes a wild-type allele of a gene to a different allele

• can result in recessive or dominant allele

reverse mutation

a mutation that causes a mutant allele to change back to the wild type

substitution

a base at a certain position in 1 strand in replaced by 1 of the other 3 bases

transition

purine replace with another purine

pyrimidine replaced with another pyrimidine

transversion

purine replaced with a pyrimidine

pyrimidine replace with a purine

deletion

the loss or black od 1 or more nucleotide pairs from a DNA molecule

insertion

the addition of 1 or more nucleotide pairs

point mutation

mutations that affect 1 or a few base pairs that only alter 1 gene

eukaryotes

organism type that have higher rates of mutation from generation to the next compared to the other

colony

a mound of genetically identical cells that all descend from a single cell

fluctuation test

experiment to determine the origin of bacterial resistance

replica plating

a process where colonies on a master plate are picked up on velvet and then transferred to media in other petri plates to test for phenotype

template

single strand of a DNA copy

primer

a short single stranded DNA molecule that is complementary to the part of the template and provides the free 3’ end to which DNA polymerase can attach new nucleotides

hybridization

base pairings between a probe and its complementary DNA sequence

chromosomes

made of a single long molecule of DNA

chromosomes

contain histone proteins, and nonhistone proteins

chromatin

complexes of DNA, protein, and RNA found in a cell’s nucleus

histone proteins

small proteins with a preponderance of the basic, positively charged amino acids lysin and arginine

histone proteins

positive charge helps them bind and neutralize negatively charged DNA

nonhistone proteins

chromatin constituents other than histones with a wide variety of functions

nonhistone proteins

some help pack DNA in structures more complex than nucleosomes

nucleosome

fundamental unit of chromatin

nonhistone protein

proteins that form the backbone of the chromosome included

nonhistone protein

proteins that are needed for chromosome segregation included

nonhistone protein

proteins that facilitate or regulate transcription during gene expression included

• influence when, where, and how frequently genes are transcribed by interacting with DNA