Unit 2 Bio Exam Review

• Cells reproduce through a continuous sequence 2 main stages; growth and division

• The first and longest stage is interphase

G1: cells carry out metabolic process to prepare  for the S phase

S: DNA replication occurs, cells can enter either the S phase or a rest phase from G1

G2: cells prepare to undergo cell division

• Then mitosis and cell division

• made up of 2 long strands that form a spiral shape called double helix

• Dna exists as strand of chromatin fiber

• Individual strands of DNA is called a nucleotide

• They are made up of phosphate group, a sugar group and a base

• Adenine (A), Guanine (G), Thymine (T), Cytosine ©

• A-t and g-c and these are called complementary pairs

• The complete DNA Structure in every cell organism is called genome

• Single chromosome is comprised of 2 sister chromatids and are held together by a centromere

• Sister chromatids are genetic copies of each othe

• In order for an organisms to replicate, grow or repair new cells are needed

• The division of the cell nucleus where daughter cells receive the exact number of chromosomes and genetic makeup as the parent cells

• 46 chromosomes are produced

chromatin condenses and thickens for form visible duplicated chromosomes

• Centrioles begin to migrate to opposite poles of the cells

• Spindle fibers begin to form between the two centrioles

Chromosomes migrate and align themselves at the middle of the cell

• Centrioles arrive at opposite poles, spindle fibers are connected

• Sister chromatids are attached to opposite spindle fibers

centromeres split and the sister chromatids are pulled to opposite poles of the spindle fibers

• spindle fibers shorten which allow pulling action to occur

mitosis is complete and 2 daughter cells are formed

• Chromatids reach opposite poles triggering telophase

• Each chromatid is now a single chromosome

• Nuclear membrane reappears

homologous chromosomes pair up forming a tetrad which consists of 4 chromatids

• Crossing over occurs

tetrads randomly align themselves along the cell equator and they line up in pairs, it's called independent assortment

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homologous pairs separate and move to opposite poles with sister chromatids remaining together therefore 1 chromosome from each pair

daughter cells are formed with each daughter cell containing only one chromosome of the homologous pair

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chromosomes condense and the nuclear envelope breaks down if needed, centrosomes move apart and the spindle fibers form between them

chromosomes line up individually along the equator (still in x)

sister chromatids separate and are pulled towards opposite poles of the cell

nuclear membrane form around each set of chromosomes and the chromosomes decondense

• Four haploid cells

Mutations: An error in the DNA sequence that can be caused by toxic compounds, radiation and or virus

• Tumors can be an example

The mutations are usually copied during prophase therefore passing the mutation to the daughter cell

• Genes that can be activated by mutations are called oncogenes

• Failure to separate chromosomes is called nondisjunction

Monosomy: one less chromone (45)

trisomy ; one extra chromosome (46)

occurs when a certain gene segment becomes free momentarily and is reinserted  in the reverse order

part of chromosome change places with another part of the same chromosome or with part of another non-homologous chromosome; can be linked to cancer

a portion of the chromosome is actually lost. Genes are lost from the chromosome. Caused by virus, chemicals and irradiation

when a gene sequence is repeated one or more times one or several chromosomes

a cross between 2 individuals in which only one trait is crossed

the genetic makeup of an organism

• the physical appearance of an organism

a cross between two individuals focusing on two specific traits

If you have an individual with a particular phenotype but whose genotype is unknown we need to perform a test cross

A chart that shows the pattern of inheritance over many generations

an inheritance pattern where the heterozygous exhibits an intermediate phenotype (blend). Neither allele for trait is completely dominant

a circumstance in which both alleles for a trait are dominant. Both alleles are expressed in hetero

a pattern of inheritance where a gene may have more than two alleles for any given trait

Some traits that are passed from one generation to the next depend on the sex of the parent carrying the trait. The transmission of genes which are located on the X or Y chromosome is called ….