Unit C

Stages of mitosis

Prophase, Metaphase, Anaphase, Telophase, Cytokinesis, & Interphase

Gap 1

cellular contents (excluding chromosomes) duplicate

Synthesis

all 46 chromosomes duplicate

Gap 2

cell checks duplicated cell for error & makes needed repair, organelles develop, prepares to divide

Prophase

centrioles go to the ends of the cell (like guide wire), condenses, nuclear membrane starts to dissolve

Metaphase

chromosomes line up at the center of the cell

Anaphase

centromeres divide, chromatids move to opposite ends of the cell

Telophase

chromatids reach ends & lengthen, spindle fibers dissolve & nuclear membrane reforms

Cytokinesis

cytoplasm begins to separate (2 new cells formed)

Centromere

area where sister chromatids are connected

Kinetochore

specialized structure on centromere to which microtubular spindle fibers attach during mitosis/meiosis

Chromatid

DNA strings, joined at the centromere

Spindle fibers

attach to chromosomes & move them by pulling homologous pairs in opposite directions

Centrioles

one pair of cellular organelles acting as anchor points for spindle fibers

Microtubules

minute tubules that pull chromatids to the centrioles

Nucleotides

Adenine, Guanine, Cytosine, & Thymine (make up DNA)

Blastula stage

stage before specialization of cells

Gastrula stage

after specialization

Telomere

protects the ends of chromosomes from deterioration/fusion with other chromosomes by allowing ends to shorten (necessary in cell division), genetic info eventually lost (age limit on life)

Apoptosis

cell suicide

Histone

structural protein in chromosome

Karyotype

complete set of chromosomes in a cell, 23 pairs homologous chromosomes, 22 pairs autosomes (not sex chromosomes)

Homologous

one member of each pair acquired from gamete of each parent

Mitosis cells

2 diploid cells result

Meiosis cells

4 haploid cells result

Unique meiosis processes

crossing over during Prophase 1, paternal & maternal chromosomes randomly assorted, different combinations of genes after fertilization

Crossing over

must be the same chromosome

Polar bodies

3 form with making of an egg, disintegrate & nutrients reabsorbed by body

Prophase 1

nuclear membrane dissolves, centriole splits & moves to poles, spindle fibers form, chromosome pairs come together as homologous pairs (synapsis), crossing over may occur

Metaphase 1

chromosomes attach themselves to the spindle, homologous pairs line up at the center

Anaphase 1

homologous pairs segregate, 1 pair of each homologous pair found in each cell

Telophase 1

nuclear membrane forms around each cell, nuclei not identical but have same traits

Meiosis 2

same as mitosis

Nondisjunction

1 pair of chromosomes doesn’t separate properly

Polyploidy

organism has more than 2 sets of chromosomes

Trisomy

organism has 3 homologous chromosomes in 1 pair

Monosomy

organism has 1 homologous chromosome in 1 pair

Down’s syndrome

aka Trisomy 21, extra chromosome at pair 21 \[almond shaped eye, flatter face, philtrum abnormalities, small ears, round/full face, short height, large forehead, flat nasal bridge, degree of cognitive impairment\]

Turner syndrome

female with only 1 X chromosome \[infertile, short stature, underdeveloped sex features, broad chest, low set ears, webbed/wide neck, low hairline, drooping eyelids, dry eyes, no period\]

Klinefelter syndromee

2 X & 1 Y chromosomes, appears male at birth, female hormones take over during puberty, infertile

Gene

2 alleles

Genotype

what’s in your genes: homozygous dominant/recessive, heterozygous

Allelephenotype

visible traits, can be used to determine genotype

Locus

physical location of a certain gene on a chromosome

Heredity

mechanisms by which traits are passed on through genes

Testcross

animal with unknown genotype is bred with known genotype to see offspring & determine genotype of unknown parent

Dominant/Recessive

all offspring appear dominant

Dominant/Heterozygous

all offspring appear dominant

Recessive/Heterozygous

50/50 split in offspring appearance

Dominant/Dominant

all offspring are dominant

Recessive/Recessive

all offspring are recessive

Heterozygous/Heterozygous

75/25 split in appearance, favoring dominant

Dominant trait examples

free earlobe, brown eyes, freckles, dark hair, dimples, widow’s peak, cleft chin

Recessive trait examples

attached earlobe, blue eyes, no freckles, blonde hair, no dimples, no widow’s peak, no cleft chin

Incomplete dominance

trait shown is between that of parents, equally dominant (ex: red flower + white flower = pink flower)

Genotypic ratio

expected ratio when certain phenotypes cross

Phenotypic ratio

visible ratio

Pleiotropic genes

effects more than 1 characteristic (ex: sickle cell anemia = higher malaria resistance)

Epistatic genes

genes that mask the expression of another gene

Multiple alleles

particular gene that exists in 3+ allelic forms, but individuals possess only 2 such alleles at same loci (ex: blood type/eye colour)

Codominance

traits both show in different cells (ex: Dalmatians)

Morgan

discovered that the farther from the centromere, the more often crossover happens, linked sex & genes using fruit fly eye colour

Marker genes

easily identifiable phenotypes

Gene mapping

distances based on frequency (process of elimination)

Dihybrid

2 independent traits (ex: eye colour & hair colour)

Crossover percentage

number of recombinations/total number of offspring x 100%

Sex linked traits

some traits are found on the X chromosome, if mother carries 50% of children will be unaffected, 50% sons will have, 50% daughters will carry (ex: colour blindness, hemophilia) both parents must have it for a daughter to have it

Sexual dimorphism

differences between sexes other than reproductive organs (ex: colour pattern in animals)

Questions for pedigrees

1) is there anyone whose phenotype is different than both parents? (yes = both parents are heterozygous) 2) are there any girls with recessive phenotype who have a father or son with dominant phenotype? (yes = can’t be sex-linked)

Polygenic

genotypes controlled by more than 1 gene (ex: chicken combs)

Continuous traits

varying degrees of variation between dominant & recessive

Continuity of Life

succession of offspring that share structural similarities with parents

Isotope

atoms of the same element containing the same number of protons, but a different number of neutrons

Radioisotope

isotope that decays spontaneously by emitting radiation

Nucleotide

molecule having 5 carbon sugar with nitrogenous base attached at its 1’ carbon & a phosphate group attached to its 5’ carbon

Deoxyribose sugar

sugar molecule containing 5 carbon

Phosphate group

group of 4 oxygen atoms surrounding central phosphorus atom found in the backbone of DNA

Complimentary pairs

Adenine-Thymine, Guanine-Cytosine

Miescher

isolated nucleic acids from pus

Griffith

Discovered that hereditary characteristics from dead bacteria could still be passed on and kill mice

Hammerling

Discovered that hereditary material much be in the nucleus

Avery & team

1944, isolated pneumococci → DNA = transforming principle. Proved Griffith’s findings on transformation

Chargaff

Discovered that the amounts of A-T and C-G were always the same is all tested organisms

Hershey & Chase

Confirmed that genetic material was carried in nucleic acid

Franklin

Used X-ray photographs and deduced the structure of DNA from that

Watson & Crick

Build a model of the double helix

DNA side structure

made of a pentose sugar, deoxyribose bonded to phosphate groups by phosphodiester bonds (merely structural, they don’t contain DNA info)

DNA center structure

made of nitrogen bases bonded together by weak hydrogen bonds

Hydrogen bonds between C & G

3

Hydrogen bonds between A & T

2

Antiparallel strands

run in opposite directions (1’ to 5’ or 5’ to 1’)

Double ring purines

Adenine & Guanine

Single ring pyrimidines

Thymine & Cytosine

Stage when DNA is copied

Synthesis stage of interphase

Leading strand

continuously replicates, from origin to the fork opening

Lagging strand

works backwards, gaps left, only a bit replicated at a time, from fork opening to the origin

Topoisomerase

untwists DNA

Helicase

cuts hydrogen bonds

Single strand binding proteins

keep strands separated

Primase

attach an RNA primer (starting point for DNA replication)