IVC Biology Unit 13-20

Helicase

unwinds the DNA

DNA polymerase

comes after the helicase and reads both sides of the DNA

Mitosis

 process in which a single eukaryotic cell replicates its DNA and divides into two new 

identical cells

• Allows a single celled organism to grow and develop into a multi celled organism 

• Allows for the repair of damaged tissue (NOT CELLS) 

• Allows for the replenishment of cell types which routinely die 

Interphase

• G1: monad DNA molecule, has various genes 

• S: DNA synthesis, replicated, mitotic spindle forms 

• G2: just the finished replicated DNA molecule, dyad form

M: cell division/cycle

• Prophase: aster is created and so are chromosomes

• Prometaphase (late prophase): nuclear envelope disintegrates, kinetochore fibers form, 

• Metaphase: chromosomes line up at the middle, at the metaphase plate, miotic is “fully formed”

• Anaphase: centrioles is torn apart and the chromosomes are split due to a protein 

• Telophase: Band of proteins begin to pinch the cell, about to split them 

  • Cytokinesis: completed split of cell

• Interphase: repeat

Monad

One single strand

Dyad

Two strands

Dominant

always expressed 

• Produces a characteristic which will be shown in the organism that possess it

• Produces a polypeptide whose effect will be exerted or shown i the organism that possesses it 

Recessive

expressed only in the absence of a dominant

• Produces a characteristic that can be overridden by a dominant

• Produces a polypeptide whose effect can be overridden by a dominant

Gene

sequence of DNA nucleotides that encodes for a specific polypeptide (protein) or mRNA

Locus

specific location along a DNA molecule at which a given gene is located

Gene pair

genes found at the same relative loci on homologous DNA molecules and that encode for the same kind of characteristic 

Allele

alternate members of a given gene pair

• An allele is a specific gene in a gene pair

Law of Allele segregation

 alleles of the same gene pair will separate from one  another during gamete formation 

Simple dominance

inheritance pattern in which there is a dominant allele in a gene pair that can completely override the recessive allele

Incomplete dominance

inheritance pattern in which neither allele in a gene pair can completely override the expression of the other allele

-two different alleles,  both of which are simultaneously expressed. (a blend)

Law of independent assortment

alleles from different gene pairs will unite in gametes in all combinations possible 

3 main sources of genetic variation

1. Prophase 1:

   1. Crossing over: creates new combination of genes on chromosomes

2. Metaphase 1, Tetrads line up at metaphase plate:

   1. Random alignment: creates different combinations of paternal and maternal chromosomes in gametes

3. Syngamy: fusion of gametes to create a zygote

   -creates new combo of genes in organisms (recombination

   -final source of genetic material

Meiosis

 produces gametes for the purpose of sexual reproduction. Process of making smaller 

• purpose of sexual reproduction is to create genetic diversity in offspring 

• Takes place in the gonads

  • testicles and ovaries 

• 46 monads - 46 dyad - 23 dyads in two cells – 23 monads in 4 different cells

• 1 diploid to 4 haploid

Meiosis 1

1. Prophase 1

   1. Crossing over: creates new combination of genes on chromosomes 

      1. -major source of genetic diversity 

2. Metaphase 1

   1. Tetrads line up at metaphase plate 

   2. Random alignment: creates different combinations of paternal and maternal chromosomes in gametes 

      1. Major source of genetic diversity 

3. Anaphase 1

   1. Separate 

4. Telophase 1

   1. Cells begin to split 

   2. Cytokinesis 

Meiosis two or Mitosis with haploids 

1. Prophase 2

2. Metaphase 2

3. Anaphase 2 

4. Telophase 2

   1. Cytokinesis 2

Pleiotropic

one gene pair/allele having multiple phenotypic effects

-ex: being albino 

Carrier

person who possesses an allele but doesn’t have the phenotype associated with it

-typically heterozygous genotype

autosomes

non-sex chromosomes

Lethal (deadly) genetic disorders

significantly shorten the lifespan of those that have them

-tay-sachs, cystic fibrosis, huntington’s disease

SRY translocation: SRY will cross over with the X,

1. During gamete production the SRY gene is transferred from the Y to the X chromosome during crossing over

2. Individual is XX but has masculine traits, that are due to the masculinizing SRY gene

   1. Have internalized testes that produce testosterone in high volumes

Sex-Linked inheritance:

More common in the males than females because males only have on X chromosome, so there cannot be a dominant gene if they get their only one x chromosome to override the recessive disorder

Polygenic conditions:

dependent upon alleles in two or more gene pairs, ex: eyes,skin, height, cognitive ability, and alcoholism  are an example (simplified is that several genes contribute to one phenotype)

Multi-allelic:

refers to a single gene pair in which there are more than 2 possible alleles 

-gene pairs for HLA (Human leukocyte associated antigen) have hundreds of possible alleles

Nondisjunction

failure of homologous chromosomes to separate 

How testosterone is produced in a man

1. Must have a Y chromosome with a function SRY gene 

2. SRY gene must now produce Testicular Determining Factor (TDF)

3. TDF must now activate genes that will code for the production of testosterone

4. Testosterone will now bind with TRPS (testosterone-receptor proteins) 

5. testosterone/TRP complexes must now activate genes that will now masculine the body

6. Must of the gene for the TRPS

Disjunction

normal separation of chromosomes

Albinism

recessive, causes someone to have very light skin, hair, and eyes. Usually have vision problems

Tay-Sachs disease

• Missing an enzyme that digests nerve cell gangliosides

Gangliosides: fatty bodies found in nerve cells of all developing humans
-have 2 recessive genes for condition

cystic fibrosis

most commonly inherited genetic illness in the united states, characterized by overproduction of mucus in lungs and other organs, recessive

Huntington disease

Lethal condition that can be passed on to offspring even though it is due to a dominant gene because it strikes the victim late in life

-stops parts of the brain working properly

-develop uncontrollable dance-like movements and abnormal body postures

Turners syndrome

Only have one sex chromosome (monosomy) (XO)

-Females who are infertile and lack brain development

-short statue if untreated

-often webbed neck

-secondary sex characteristics don’t develop

-due to chromosomal non-disjunction

Klinefelter’s syndrome

XXY, Males, Male characteristics at puberty don’t develop

-can lead to infertility and mixed male and female expression

-due to chromosomal non-disjunction
-trisomy

down syndrome

which a person has 47 chromosomes, with 3 (trisomy) rather than 2 chromosomes at the 21st site.

-distinctive characteristics like unusual facial features, heart abnormalities, hearing problems, muscle weakness, short stature,  and language difficulties 

-thick tongue round face, slanted eyes

-cognition and language develop slowly with notable challenges in the ability to rhyme

-have fewer internalizing problems (depression)

-due to chromosomal non-disjunction

Ecology

Scientific study of how organisms interact with each other and with their nonliving environment

Ecological niche

 manner in which an organism uses the resources in and is influenced by the conditions of its habitat

• Determined by an organism's physical adaptations (structural, behavioral, or chemical)

Physical adaptations:

genetically inherited characteristics that enable a given organism to survive and reproduce using a given niche

Resources

 material that is used and potentially used up (food,  water, nesting materials, open space, shelter, etc.)

Habitat

physical place, or  type of place, where an organism lives

Conditions

background features of the habitat (temp, humidity, salinity, altitude, irradiance, pH, etc)

Competitive exclusion principle:

Gauses Principle, No two species can use the same niche in the same habitat

• One or the other, or both, will inevitably be outcompeted

Competition:

antagonistic struggle for a common resource, 

• win the resource: you lose, you lose time, energy, other opportunities, tissue, and life

• Lose the resource:  you lose, you lose time, energy, other opportunities, tissue, and life

Niche partitioning:

division of niches between species so as to cut down on competition 

• Can be permanent or temporary

Fundamental niche

largest array of resources an organism can utilize

Realized niche:

actual set of resources utilized 

• Resorted to when competition with other species sets in, and must be avoided 

Populations

 individuals within a species interact with each other as members of a population or  colony 

-group of organisms of the same kind that actually or potentially interbreed so as to produce viable offspring 

Exponential (population growth)

as on the j-shaped growth curve, lag phase and acceleration phase

1. At a fixed rate per time period

Logistic (population growth

1. as on the S-shaped growth curve, longer lag, acceleration, deceleration, equilibrium

Biotic potential

maximum reproductive capacity of a population in the absence of environmental resistance

Environmental resistance

 ecological features that inhibit population growth 

• Density independent: drought, hot spells, cold snaps, fires, floods

• Density dependent: predators, disease, food shortages, water shortages, build up of wastes, lack of space

Carrying capacity

environments ability to hold a specific number of individuals for a prolonged period of time

environmental/natural selection:

 violates no reproductive or survival advantage to any gene/genotype, survival of individuals in a population, which leads to differential survival of genes, can create trends in allele frequency shifts

Gene pool

all of the inheritable alleles found within a given population

gene/allele frequencies

numeric rate at which a gene/allele occurs in a gene pool relative to the other alleles in its gene pair

Hardy Weinberg equilibrium rules:

gene frequencies within populations will remain stable over long periods of time if the following conditions can be met

1. Must be no random events that differential eliminate alleles

2. Must be no migration into or out of the population

3. Must be no reproductive or survival advantage to any gene or genotype

4. All mating must occur at random (no selection criteria for mates)

5. Mutations (Alteration to the nucleotide sequence of a gene)  may not occur 

   1. Causes: exposure to radiation, toxins (ionic compounds), random replication errors in DNA synthesis 

Gene drift

Violates no random events, changes in gene (allele) frequency owing to random factors

Gene flow:

violates no migration, movement of genes (alleles) into or out of population resulting from migration

Evolution

changes in gene frequencies in populations over time

Sexual selection

violation of all mating must occur at random, mate pairing criteria create differential survival and replication of specific alleles 

Sexual reproduction:

can create new combos of genes but by itself, can’t change gene frequencies

Evolutionary fitness:

ability of an organism or allele to survive and reproduce relative to other individuals or alleles within the population

Genetic diversity

variety of genes/genotypes in a gene pool, environmental selection acts to eliminate genes. Only certain genes can survive in a given environment

Stabilizing selection:

No genetically related change in population mean over time, selective pressure keeps population centered around an average 

Directional selection

genetically related change in mean over time follows a progressive trend, selective pressure moves population from one average to another 

Disruptive selection

genetically related change in mean over time produces two “means” (modes), selective pressure splits population around two “averages” or modes

species

 population of organisms which is reproductively isolated from other populations of organisms

Reproductive isolation

inability of populations to interbreed such as to produce a merger of separate gene pools 

Speciation:

 evolution of reproductive isolation in two populations which previously interbred, disruptive selection is the only selection pattern that can produce speciation

Allopatric

speciation occurs in two separate areas, usually involves some geographic barrier (river, canyon, etc)

Sympatric

speciation occurs in the same area, usually involves some sudden mutation

Parapatric

speciation occurs in two adjacent areas

Prezygotic

two species don’t mate with each other such as to produce a fusion of gametes 

1. Habitat: two species reproduce in different habitats 

2. Temporal: two species mate at different times of the year, or day

3. Behavioral: songs, dance behaviors, visual cues (just mating calls) 

4. Mechanical: breeding is prohibited due to anatomical constraints 

5. Gametic incompatibility: egg and sperm cells don’t chemically recognize each other

post-zygotic

isolation occurs even after the egg and sperm have fused, after mating, fertilization, and syngamy have occurred 

1. Hybrid (zygote) mortality: sperm and egg fuse, but the offspring fail to develop

2. Hybrid sterility: two species mate, produce offspring,  but the offspring aren’t fertile

3. Hybrid inviability: hybrid offspring can’t survive long enough to reproduce 

mutations

Alteration to the nucleotide sequence of a gene