Exam 4 Flashcards
DNA replication
- the amount of DNA in a cell is doubled
- part of the preparation for the cell to divide
DNA replication is semiconservative..
after one round of DNA replication the daughter DNA molecules are formed of one paternal and one daughter strand
DNA Polymerase 3
enzyme in charge of DNA replication, synthesizes the daughter strands
what are the three features of DNA polymerase 3?
- only synthesizes the daughter strand from 5’ to 3’, the template strand from 3’ to 5’
- needs an available/free 3’ end = cannot start synthesis by itself
- needs single stranded DNA
steps for synthesis of the leading strand
- helicase: breaks H-bonds between parental strands
- SSBP’s (single-strand binding protein): attach single strand DNA and prevent H-bonds from reforming
- topoisomerase: relieves tension from twisting forces, sits in front of replication fork
- protein primase: synthesizes a short sequence of RNA (primer)
- DNA polymerase 3: uses the 3’ end to continue the synthesis of the leading (daughter) strand from 5’ to 3’
leading strand
synthesized from 5’ to 3’
in the same direction as the replication fork
synthesized in one continuous piece
lagging strand
synthesized from 3’ to 5’
opposite direction as the replication fork
synthesized in fragments called Okasaki Fragments
origin of replication
sequence that indicates where to begin DNA replication
replisome
“posse” in charge of DNA replication
- collection of seven proteins
replication fork
where DNA synthesis is happening
chromosomes
DNA + histones (proteins); discrete units of genetic information
chromosomes in eukaryotic cells versus prokaryotic cells
eukaryotic cells: chromosomes are linear and there is more than 1 type
prokaryotic cells: chromosomes are circular and usually 1 type
gene
sequence of DNA that encodes for one characteristic
- found in chromosomes in specific locations
in organisms that reproduce sexually..
one is inherited from the maternal side and the other from the paternal side
homologous chromosomes
maternal and paternal of the same chromosome type
- same order of genes, shape, and size
sister chromatids
two identical chromatids that are joined together
* as long as they are attack they count as ONE CHROMOSOME
karyotype
shows all chromosome types
- humans have 23 types
sexual chromosomes (X,Y)
carry information to determine biological sex of an individual
autosomes
do not carry information that determines the biological sex of an individual
n
the number of distinct chromosomes in a species
- humans n = 23
somatic cells
cells that do not participate in sexual reproduction
- ex diploid = 2n
diploid
carry two sets of chromosomes (homologous chromosomes)
- one set is paternally inherited and the other set is maternally inherited
- in humans 2n = 46
gametes (sex cells)
cells that participate in sexual reproduction
- ex haploid = 1n
haploid
one copy of each distinct chromosome
- one set of chromosomes
- in humans 1n = 23
cell cycle
events/phases in the life of a cell
what are the phases of the cell cycle?
G1, S, G2, and M phase
G1 phase (gap phase)
- cell grows
- acquires nutrients
- multiplies organelles
- does its “job”
S phase (synthesis)
- DNA is replicated
- sister chromatids form
G2 phase
cell prepares for cell division
M phase (mitosis)
mitosis: nuclear division
cytokinesis: cytoplasmic division
cell cycle checkpoint
regulatory point in which the cell assesses whether it is ready to progress to the next step
what are the four cell cycle checkpoints?
- G1 checkpoint
- G2 checkpoint
- metaphase checkpoint
- anaphase checkpoint
G1 checkpoint
- is cell site adequate?
- are there enough nutrients?
- is DNA undamaged?
G2 checkpoint
- did the chromosomes replicate correctly?
- is the DNA undamaged?
metaphase checkpoint
- are the chromosomes attached to the spindle correctly?
anaphase checkpoint
- did the chromosomes separate correctly?
mitosis
produces two daughter cells that are genetically identical to each other and to the parent cell
what is the purpose of mitosis
unicellular organism: asexual reproduction
multicellular organism:
- growth (adding new cells)
- cell replacement
- wound repair
- asexual reproduction (in some trees)
what are the steps of mitosis?
- prophase
- pro-metaphase
- metaphase
- anaphase
- telophase
prophase
- chromosomes condense
- nuclear envelope begins to break down
- spindle begins to form
pro metaphase
- spindle is complete
- nuclear envelope is gone
- microtubule attack to chromosomes
metaphase
chromosomes align in the metaphase plate
anaphase
sister chromatids separate
telophase
- spindles disappears
- 2 nuclear envelopes form
- chromosomes decidedness
animals: cleavage furrow forms
plants: cell plate forms
cytokinesis
complete division of cytoplasm
spindle apparatus (mitotic spindle)
temporary structure that organizes and sorts chromosomes during cell division
- made of microtubules that is part of the cytoskeleton
cytokinesis in animal cells
occurs by cinching the plasma membrane
- the cell builds a ring of actin- attached to the inside of plasma membrane
- the ring becomes smaller and forms the cleavage furrow which eventually separates the two cells
cytokinesis in plant cells
each daughter cell builds its wall and membrane
cell plate formation:
1. Golgi synthesizes cell wall materials and puts them inside vesicles
2. vesicles migrate to the middle
3. vesicles fuse and release cell wall materials, starts to build plasma membrane
cancer
series of diseases that vary on the age of onset the location in the body, the changes of survival
what is the cause of cancer?
mutations in the genes that regulate the cell cycle
- involved checkpoint failures
what are the steps of cancer?
- cell mutation - dividing factor > 2.tumor (located= benign) - more mutations> 3. malignant tumor (cancer) - metastasis (spread to other parts of the body) > 4. multiple tumors
meiosis
- produces 4 genetically different gametes (haploids)
- determines genetic information in gametes
- consist of two rounds of division meiosis 1 and 2
life cycle between meiosis and mitosis in an individual
- meiosis: # of genetic info is cut in half
- egg/sperm (haploid)
- fertilization (amount of genetic info is restored)
- zygote (2n)
- mitosis (development)
- adult - then repeats
meiosis 1
homologous chromosomes separate
1 diploid turns into 2 haploid (half amount of chromosomes)
meiosis 2
sister chromatids separate
2 haploid turns into 4 genetically different haploid (same amount of chromosomes)
crossing over
exchange between non-sister chromatids within a pair of homologous chromosomes
- takes place in prophase 1
- source of genetic variation
independent assortment
chromosomes sort at random during meiosis 1 between daughter cells
- independent of whether they are maternal or paternal
2n = 6 how many chromosomal combinations
- 6/2 = 3 chromosome types
- 2^3= 8 chromosomal combinations
fertilization
gametes (egg and sperm) fuse at random
down syndrome
an example of an error in meiosis that is a trisomy
trisomy
three copies of one chromosome
monosomy
a lack in one chromosome
non disjunction
error in meiosis that happens when homologous chromosomes do not separate correctly during meiosis 1 and/or sister chromatids do not separate correctly during meiosis 2
fertilization + non disjunction
n (normal gamete) + n+1 gamete = 2n + 1 zygote (trisomy)
or
n + n-1 = 2n - 1 (monosomy)
chromosome theory of inheritance
- DNA is genetic material that are organized in chromosomes that contain genes
- chromosomes are inherited from parents to offspring
- diploid cells contain pairs of homologous chromosomes (paternal and maternal set)
- during meiosis 1 homologous chromosomes assort independently regardless of maternal or paternal
- gametes are haploid
character
characteristics common to a species that is heritable
* controlled by genes*
varaints
traits that are controlled by alleles
alleles
variations of genes
examples of characters, variants, and alleles in pea plants
character: flower color
variant (trait): purple or white
allele: 1 gene for purple and 1 gene for white
phenotype
observable/measurable traits in an individual
- outcome of the genotype
genotype
description of the genetic make up of an individual
dominant
is always expressed
recessive
is only expressed when paired with another recessive allele
homozygous
both of the same allele
* homozygous dominant: both alleles are dominant
* homozygous recessive: both alleles are recessive
heterozygous
both alleles are different
single-factor cross experiment
classic Mendelian experiment that involves one character
punnett square
tool for determining the outcome of a genetic cross
genotypic ratio steps
- write every possible genotype: TT, Tt, tt
- count how many cells have that genotypes: 1 TT: 2 Tt: 1tt
phenotypic ratio
- write all possible phenotype: tall or dwarf
- count how many cells have that phenotype: 3 Tall: 2 dwarf
principle (law) of segragation
each gamete carries only one allele per gene
