BSC2010 Exam 2 UF

heredity

the transmission of biological traits from parent to offspring and from generation to generation

chromosomes

threadlike structures containing proteins and nucleic acids

sister chromosomes

the duplicated chromosome and the template chromosome

centromere

when sister chromosomes remain attached at a common point of attatchment

homologous chromosomes

occurs during mitosis when sister chromosomes separate

No, they are not identical, they just carry genes for the same inherited characteristics

Are homologous chromosomes identical?

mitosis

cell division in somatic cells, which produces daughter cells with exact replica of the parents' DNA

somatic cells

the body's nonproductive cells, which have two sets of chromosomes

meiosis

cell division in germ cells, which produces daughter cells with DNA different from the parents' cell DNA

An organism's lifespan is linked to cell ____________

division

Reproduction

unicellular organisms can reproduce through cell division

Growth

organisms can get larger through cell division

Regeneration

some organisms can regenerate entire body parts through mitosis

4 General Steps in Cell Division for both prokaryotes and eukaryotes:

1) Signal to initiate- cell receives some signal to initiate cell division
2) Replication of DNA- cell's DNA replicates
3) Segregation- cell's DNA segregates into 2 new cells
4) Cytokinesis- cytoplasm is divided and the two new cells split apart

binary fission

how prokaryotes undergo cell division, offspring are generally clones (identical) of the parent

1) Signal to initiate - Cell receives some signal to initiate cell division
2) Replication of DNA - Cell's DNA replicates
3) Segregation - The cell's DNA segregates into two new cells
4) Cytokinesis- Cytoplasm is divided, and the two new cells split apart

Process of binary fission:

Whereas _________ have only one chromosome, __________ have multiple chromosomes.

prokaryotes; eukaryotes

What is the human body's chromosome number?

46 total chromsomes

ploidy

refers to the number of homologous chromosomes that exits for each chromosome type

haploid

only has one chromosome for each chromosome type ( ex: human gametes)

diploid

has two homologous chromosomes for each chromosome type ( ex: human somatic cells- 23 chromosomes from mother and 23 from father)

sister chromatid

when two chromatids are joined together at a common centromere

centromere

the region of the chromosomes to which microtubules attach during cell division)

Once mitosis has occurred, the _______ __________ separate, they duplicate and then two new chromosomes result

sister chromatids

nucleus

surrounded by a membrane and contains the genetic material (DNA)

chromatin

what DNA is packaged by (special proteins)

nucleolus

synthesis of ribsomes

centrosomes

regions near the nucleus that are associated with the formation of spindle fibers and spindle poles during mitosis

cytoskeleten

"internal scaffolding", constructed of microtubules, microfilaments, and intermediate filaments, provides structure and support for the cell

cell cycle

refers to the period between successive cell divisions

Interphase

refers to any portion of the life of a cell in which mitosis is not occurring

During Interphase, the cell synthesizes __________, produces _________, and grows in _________.

RNA, proteins, size

condensed

During Interphase, DNA Replication occurs, but ___________ DNA is not visible yet.

Interphase can be divided into 3 phases:

1) Gap 1 phase (G1): cell grows and produces RNA and protein
2) Synthesis (S) phase: DNA is duplicated through DNA replication
3)Gap 2 phase (G2): preparation for mitosis

mitotic phase (M phase)

process by which a parent cell divides into 2 daughter cells; consists of two phases: mitosis and cytokenisis

nucleus, cytoplasm

Mitosis refers only to the division of the ___________, whereas cytokinesis refers to the division of ___________.

Prophase

step during which the nucleolus fades, chromatin begins condensing into chromosomes, microtubules of the cytoskeleton dissemble, and meiotic spindle forms

Prometaphase

step during which nuclear envelope is dissolved completely and some spindle fibers attach to kinetochores

Metaphase

chromosomes align on the metaphase plate at the cell's center

Anaphase

chromatids pull apart (pulled apart by separase enzyme) and being moving to cell poles as the spindle fibers shorten, cell elongates during this phase also

Telophase

spindle breaks down, the nuclear envelope and nucleoli being to reform and chromosomes uncoil and become less compact. At the end of this phase, 2 daughter nuclei with identical genetic information are formed

cytokinesis

After mitosis, during __________, the cytoplasm divides and 2 independent cells are formed

If chromosomes do not properly line up in metaphase, __________ will not proceed.

mitosis

asexual reproduction

genetic information is passed on from parent to offspring and offspring is identical; favorable when there aren't many available mates (also advantageous in places where there are existing genes in the population)

sexual reproduction

only occurs in multicellular eukaryotes; 2 individuals contribute half of their genetic material to offspring (offspring are genetically different from parent)

meiosis

necessary for sexual reproduction and formation of gametes; forms haploid cells from diploid cells, also key in genetic variation

different

Sexual reproduction has an evolutionary advantage over asexual reproduction because the offspring are genetically ___________ from their parent.

in humans, gametes are the only ________ structure, whereas everything else is ________

haploid; diploid

meiosis 1 (the reductional phase)

homologous chromosomes separate and the cell divides, forming 2 haploid cells with 2 sister chromatids of each homologous chromosome

prophase 1

a synaptonemal protein complex attaches the homologs, and the homologs form a tetrad, in late prophase 1, DNA is exchanged between homologs at the chiasmata, which is formed as chromosomes cross over each other (important for genetic variation)

metaphase 1

chromosomes line up in middle independently; gives rise to independent assortment

anaphase 1

homologous chromosomes of each tetrad separate and move along spindle fibers toward each pole as kinetochore tubules shorten

telophase 1

homologous chromosomes reach opposite poles and there is haploid complement of chromosomes at each pole, new nuclear membrane surrounds each haploid set

cytokensis

pinching of cell membrane- completes creation of 2 daughter cells

meiosis 2 (the equational or restoration phase)

the sister chromatids separate and the cells further divide into 4 haploid daughter cells with a single chromosome (very much like mitosis)

prophase 2

chromosomes condense and spindle forms

metphase 2

chromosomes meet at metaphase plate in middle and spindle fibers attach to kinetochores of sister chromatids

anaphase 2

centromeres of sister chromatids separate and sister chromatids move to opposite poles, they are now called chromosomes

telophase 2 and cytokensis

result in the splitting of the cell into 2 daughter cells and the chromosomes uncoil, total of 4 haploid gametes are formed

crossing over only occurs in meiosis ____, not in meiosis _____.

1;2

haploid

mitosis is diploid and meiosis is _________

mitosis has one cell divisions but meiosis has ____

two

mitosis produces 2 daughter cells, but meiosis produces ____

four

mitosis doesn't have crossing over but _______ does

meiosis

independent assortment of chromosomes occurs during ____________ of meiosis

metaphase 1

independent assortment randomly mixes chromosomes producing genetic variation without using any _____-________

crossing -over

crossing over of chromosomes

occurs during prophase 1 of meiosis 1, also results in genetic variation, also leads to unimaginable increase in the number of possible gametes and offspring that can result through meiosis and subsequent fertilization)

nondisjunction

occurs when homologous pairs fail to separate in anaphase 1 or when sister chromatids fail to separate in anaphase 2

nondisjunction results in gametes with an _______ number of chromosomes

abnormal

aneuploidy

a chromosomal abnormality in which a person has an abnormal number of chromosomes in his or her genome

monosomy

one chromosome lacks a homologous partner

trisomy

when there are three copies of one chromosome type rather than two

trisomy 16 is common for ________ and trisomy 21 is ____________.

miscarriages; down syndrome

polyploidy

chromosomal abnormality in which a person has an abnormal number of chromosome sets; can result from an extra round of DNA replication before meiosis or lack of spindle formation in meiosis 2

Gregor Mendel

father of genetics; studied pea plants

Why are pea plants good to test with?

1) It is easy to do controlled crosses with peas (they are self-fertile)
2) there are many variety of pea plants which bred true for particular traits (different colors and shapes)
3) there are discrete variables to look at (green or yellow, round or wrinkled)
4)there are no gene-environment interactions

parental (P) generation

first generation of a cross

first filial generation (F1)

offspring of the parental generation

second filial generation (F2)

grand-offspring of the parental generation

genes

"heritable factors" that Mendel discovered

alleles

alternative versions of genes

locus

a physical location on a chromosome

homozygote

when the alleles in the homologous pair is the same

heterozygote

when the alleles in the homologous pair is different

Law of Segregation

occurs during meiosis 1 when the two alleles at a locus segregate such that each gamete gets only one of the alleles

punnett square

tool invented by Reginald Punnett to determine probability that an offspring will have a particular genotype

test cross

involves crossing your organism with a known homozygous recessive

Law of Independent Assortment

states that alleles at each locus segregate independently of other alleles at other loci during metaphase 1 of meiosis 1; NOTE: this law only holds true when the alleles are on different chromosomes; only applies to unlinked genes

monohybrid cross

a cross between two individuals who are identically heterozygous for a single trait on single locus

dihybrid cross

a cross between two individuals who are identically heterozygous for two separate traits at separate loci

sex linkage "X-linkage"

occurs when a gene resides on a sex chromosome, so the phenotypic expression of the trait that the gene controls depends on the gender of the individual

___________ are more likely to express the recessive condition than _________

males; female

the _____ chromosome is much smaller than the _______ chromosome; therefore, there are more genes on the ____ chromosome

Y;X;X

males usually only have _____ functional copy of a gene on a sex chromosome (therefore, they have the recessive trait more than females)

one

Characteristics of X-linked recessive phenotypes

1) more common in males than females
2)affected males can only pass on mutation to daughters, not sons
3) daughters who receive only one recessive allele are heterozygous carriers
4)mutant phenotype can skip generations

pedigree

a diagram showing the occurrence of heritable characteristics in parents and offspring over multiple generations

autosomal dominant

offspring can only be affected if one of the parents is affected (two unaffected parents can't produce affected offspring)

autosomal recessive

if 2 unaffected parents have an affected offspring, the trait must be recessive (often skips generations)

sex-linked dominant

affected fathers pass the trait on to all their daughters, all affected sons have an affected mother (females often more affected than males)

sex-linked recessive

more males are affected than females, and all daughters of affected fathers are carriers (often skips generations)