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chromosomes
made up of condensed chromatids
chromatin
a cell’s genetic material
histones
proteins that chromatin coils around
genes
code for specific proteins to create certain characteristics in an organism
chromatid
each half of a duplicated chromosome
centromere
keeps the chromatids together and breaks them apart at the right times
sex chromosomes
determine whether an organism will be male or female
the two human sex chromosomes
X and Y
autosomes
chromosomes that don’t determine an organism’s gender/sex, contains most of the organism’s genes
humans have __ autosomes
44
humans have __ sets of autosomes
22
karyotype
an image of ordered chromosomes taken under a microscope
homologous
having the same proportions
diploid
organisms that have homologous pairs of chromosomes
haploid
organisms with just one set of chromosomes
diploid cell =
2n
haploid cell =
n
cell cycle
the process of cell growth
the three stages of the cell cycle
interphase, mitosis, and cytokinesis
interphase
phase where the cell spends most of its time. at the end of interphase, the tetraploid cell with its extra organelles, proteins, and chromosomes is ready for mitosis and cytokinesis
the four phases of mitosis
prophase, metaphase, anaphase, telophase
prophase
the centrosomes are carried to opposite ends of the cell by protein motors, then are assembled with fibers from the cytoskeleton into the mitotic spindle, chromatin coils into visible chromosomes in the nucleus, the nucleolus is disassembled, and the membrane around the nucleus breaks down to release the chromosomes
mitotic spindle
a structure formed during prophase that align and separates chromosomes in later phases
metaphase
begins when the mitotic spindle fibers attach to the proteins on the centromere of each chromosome, pull the chromosomes to align them along the equatorial plane
equatorial plane
an imaginary line that goes down the cell
anaphase
the centromeres send out signals to split the centromeres in half, the mitotic spindle pulls the chromatids towards the centromeres
telophase
the chromatids are now their own chromosomes, the nucleus begins to reform around them, nucleolus begins to reassemble and the chromosomes uncoil to become chromatin again, mitotic spindle in the cytoplasm assembles
cytokinesis
the cell divides the contents of its cytoplasm, forms a contractile ring between the two nuclei, pinches them into two separate cells, resulting in two genetically identical daughter cells
contractile ring
forms around the cell and splits it into two
meiosis
occurs during sexual reproduction, forms haploid gametes, doubles the chromosomes and cytoplasmic proteins and organelles
phases of meiosis
prophase I, metaphase I, anaphase I, telophase I, cytokinesis, prophase II, metaphase II, anaphase II, telophase II, cytokinesis
prophase I
membrane around the nucleus dissolves, chromosomes join to make tetrads, exchange genes in the process of crossing over, centromeres migrate and spindle forms
metaphase I
spindle fibers align tetrads on equatorial plane
anaphase I
spindles separate each tetrad and pulls whole chromosomes towards the centromeres instead of individual chromatids
telophase I and cytokinesis
nucleus reforms around each haploid chromosome set, cytoplasm is divided, cell is pinched into two
prophase II
immediately after cell division, spindle re-forms to begin meiosis II
metaphase II
spindle fibers align chromosomes on equatorial plane
anaphase II
chromosome centromeres split, spindles pulls chromatids towards centromeres
telophase II and cytokinesis
the nucleus re-forms around the haploid chromosome sets, resulting in four genetically different cells
Average human and mammal cells take about ______ to go through the cell cycle
24 hours
gametes
haploid cells that unite to form zygotes
zygotes
a diploid cell that is genetically different from either parent
asexual reproduction
a process that produces offspring that are genetically identical to their parents, used by many plants
sexual reproduction
a process that occurs when two haploid cells join to form a genetically different diploid zygote
heredity
the passing of traits from one generation to another
factor
contributed by both parent plants
dominant traits
expressed trait
recessive traits
the trait that isn’t expressed
alleles
the different forms a gene can have
homozygous
has the same alleles for a trait; purebred
heterozygous
has two different alleles for a gene; hybrid
genotype
an organism’s genetic makeup
phenotype
the physical expression of a trait
Punnett squares
squares drawn that show different ways alleles can segregate
monohybrid cross
a cross that only tests one set of alleles
dihybrid cross
the crossing of two sets of alleles
pedigree
a family history that charts a hereditary trait through past generations
incomplete dominance
the blending of alleles
codominance
when both alleles are expressed
example of multiple alleles
human blood type
polygenic inheritance
two or more genes working together to express a trait
sex-linked traits
traits determine by the sex chromosomes
most of an organism;s traits are determined by its _____
autosomes
carriers
organisms that carry an allele but don’t express it
gene expression
the process in which genetic information is activated to make a genetic product
promoters
little sequences of DNA that come before each gene and tell the RNA polymerase molecule where to bind to begin copying the gene into a strand of mRNA
TATA box
a promoter that binds to a group of transcription proteins that are attached to RNA polymerase
enhancers and silencers
attach to promoters in front of genes and act like switches
hormone-activated traits
when hormones bind with the DNA during transcription and activate genes that had not been activated before
transcription can be affected by:
light, temperature, hormones, chemicals
cell differentiation
the process in which zygotes are changed to perform more specialized tasks
totipotent
the cell has the potential to be any kind of cell
pluripotent
the cell is capable of producing many kinds of cells but not all
homeotic genes
a special set of genes in a baby’s cells that produce each kind of cell needed
stem cells
cells that have not differentiated into specialized cells
embryo
the early stage of an unborn young of a multicellular organism
somatic stem cells
“adult” stem cells
