genetics unit 1

when did genetics start

8000-`1000 BC with domestication of horses camels, wolves, maize, wheat, rice etc

hippocratic school of medicine and Aristotle tried to explain heredity using the concept of

active humors and vital heat

in the 1600s William Harvey gave what theory

• epigenesis

• an organism develops from fertilized egg

• contrasts with preformation, fertilized egg contains mini adult called a homunculus

cell theory

scheiden and Schwann

• proposed that all living organisms are composed of cells and that the cell is the basic unit of life. This theory laid the foundation for modern biology.

natural selection is the driving force for

adaptation

existing species arise from ancestral species by

descent with modification.

the theory of evolution by natural selection was independently was also proposed by

Alfred Russel Wallace.

what did Darwin and Wallace not understand

mode of inheritance

gregor Mendel offered an explanation of inheritance by using

peas

the chromosomal theory of inheritance

• sutton and boveri

• states that inherited traits are controlled by genes residing on chromosomes

• noticed that behavior of chromosomes during meiosis was identical to behavior of genes during gamete formation

_______ explains how genetic information is passed onto the next generation

The theory of inheritance

Avery Macleod and McCarty showed

that dna carried genetic information in bacteria

Hershey and chase showed

that dna carried genetic information in bacteriophage

Watson and crick 1953

discovered the double helix structure of DNA, revealing how genetic information is stored.

dna is an antiparrale double stranded helix

• nucleotide

• four bases of adenine cytosine guanine and thymine

dna is made up of

sugar, nucleotide, phosphate

transcription

DNA to RNA

transcription occurs in the

nucleus

after transcription occurs in the nucleus

the mrna moves into the cytoplasm where it binds to a ribosome

when the mrna binds to the ribosome it is then turned into

a protein through translation.

what are the largest category of proteins

enzymes

once a protein is made its action or location in a cell plays a role in producing

phenotype

alternate forms of genes are called

alleles.

variation in alleles are the result of

mutations

a set of alleles for a given trait is called

genotype.

restriction enzymes discovered in bacteria that cut viral dna at specific sequences describes

recombinant technology

with the use of _____ restriction enzymes have allowed the advent of recombinant DNA and cloning

vectors

model organisms have what traits

• easy to grow

• short life cycle

• many offspring

• genetic analysis is straight forward

what allowed us to see eukaryotic cell structures

development of the transmission electron microscopy in the 1940s-60s

prokaryotic cells do not have

golgi, ER nucleus or membrane-bound organelles

a= metacentric

b= submetacentric

c= acrocentric

d= telocentric

A=p arm

B=q arm

haploid numbers can

vary extensively

humans have how many autosome pairs

22

dogs have 39 chromosomes and what does this mean

not that their genome is bigger, just that they are split up in more fragments

homologous chromosomes

same size and their centromere is the same location

they code for the same genes, but they have different alleles

the basis for asexual reproduction in many single celled organisms

mitosis

the development of a zygote into an adult through mitosis is called

asexual reproduction

wound healing, blood and skin cell production and tumor development occurs through

mitosis

the typical human cell has a cell cycle that lasts

24 hours

the cell cycle process

G1 → S → G2 → M

G0 step

the non dividing phase, where cells can opt out of the cell cycle either permanently or temporarily

interphase includes

S phase

two gap phases (G1 and G2)

G0 withdrawal from the cycle

G1

• cell growth

• metabolic activity

• cell differentiation

• no DNA replication

S phase

• cell growth

• metabolic activity

• cell differentiation

• DNA replication

G2 phase

• cell growrth

• metabolic activity

• cell differentiation

• no DNA replication

when do cells enter G0 or commit to entering the S and completing another cell cycle

in late G1

______ cells are characterized by uncontrolled cell division, they apparently never enter G0 or they pass through it very quickly

Cancer

chromosomes are extended and uncoiled forming chromatin

interphase

chromosomes coil up and condense; centroioles divide and move apart

prophase

chromosomes are clearly double structures; centrioles reach the opposite poles; spindle fibers form

pro metaphase

chromosomes align on metaphase plate

metaphase

centromeres split and daughter chromosomes migrate to opposite poles

anaphase

daughter chromosomes arrive at the poles; cytokinesis commences

telophase

factors of prophase

• migration of centrioles to establish poles

• break-down of nuclear envelope

• disintegration of nucleolus

• chromosome condensation

migration of chromosomes to metaphase plate happens during

prometaphase and metaphase

movement of chromosomes happens in _____ where completion of movement happens in

prometaphase metaphase

which phase do sister chromatids separate and migrate to opposite ends of the cell and requires kinetochore and spindle fiber attachment

anaphase

telophase factors

• cytokinesis

• chromosomes begin to uncoil

• nuclear envelope reforms

• single fibers disappear

• nucleolus reforms

chromosome

chromatin

folded fiber model

• two sister chromatids joined at centromere

• each chromatid is a single fiber wound like a skein of yarn

• fiber is tightly coiled DNA and protein

• 5000x compaction in the length of the DNA during transition from interphase to prophase

_____ produces two daughter cells that are genetically identical to their parent cell

Mitosis

_____ produces four gametes or spores with only a haploid set of chromosomes

Meiosis

______ is highly specific because each gamete must contain precisely one member of each homologous pair of chromosomes

Meiosis

when do two gametes fuse to reconstitute a diploid complement of chromosomes

during sexual reproduction

the two features of meiosis generating variation

• segregation and independent assortment of maternal and paternal chromosomes during Meiosis I

• crossing over or genetic exchange between members of a homologous pair

meiosis consists of how many rounds of duplication and how many rounds of cell division resulting in haploid cells

one round of cell duplication and two rounds of cell division

meiosis reduces the amount of genetic material by one half to produce haploid gametes or spores containing one member of each _____ of chromosomes

homologous pair

what restores the diploid number in meiosis

fertilization

how does meiosis maintain genetic continuity from generation to generation and gives rise to genetic variation in gametes

• crossing over

• unique combinations of maternal and paternal chromosomes

when do sister chromatids separate

anaphase II

In humans, what is a fundamental difference between the production of female gametes and male gametes?

During the production of female gametes, one daughter cell contains most of the cytoplasm, and two or more polar bodies contain only a small amount of cytoplasm.

What is the significance of the formation of polar bodies?

Polar bodies allow for the unequal distribution of cytoplasm during oogenesis, ensuring that the ovum has sufficient resources for early development.

meiosis begins with

diploid cell - dna duplicated during interphase, chromosomes made up of sister chromatids

prophase I is a process similar to mitotic prophase, except that

homologous chromsomes pair up (synapsis)

______ gives rise to a tetrad with overlapping of non sister chromatids

synapsis (prophase I)

tetrad

two pairs of sister chromatids

during prophase I there is an exchange of genetic material through

recombination

what happens in prophase I

• nuclear envelope and nucleolus break down

• two centromeres of the tetrad attach to the spindle fibers

what happens in metaphase I

• chromosomes have maximally shortened and thickened

• chiasmata are visible and holding sister chromatids together

alignment of chromosomes at the metaphase plate is random; half of each tetrad is pulled randomly to opposite poles…. which phase is this?

Anaphase I

what is marked with the reappearance of the nuclear membrane and a short interphase?

telophase I

chromosomes do not replicate because they already consist of sister chromatids…. which process is this?

meiosis I

what is the ploidy of cells in meiosis I at the end

haploid

prophase II

chromosomes are composed of one pair of sister chromatids attached by a common centromere

metaphase II

centromere is positioned at the metaphase plate

anaphase II

centromeres divide; sister chromatids are pulled to opposite poles

telophase II

similar to mitotic telophase

• cytokinesis results in four haploid gametes with equal cytoplasm containing combination of maternal and paternal genes

male vs female gamete production

spermatogenesis and oogenesis

in spermatogenesis an undifferentiated germ cell called ______ enlarges to become a primary spermatocyte

spermatogonium

in spermatogenesis the primary spermatocyte undergoes meiosis I to produce ________

HAPLOID secondary spermatocytes

secondary spermatocytes under go meiosis II to produce ________ that undergo a series of developmental changes, ______ to become highly specialized, motile spermatozoa or sperm

four haploid spermatids; spermiogenesis

an undifferentiated germ cell called an _____ enlarges to become a primary oocyte

oogonium

meiosis I of oogenesis results in

one haploid secondary oocyte and one polar body

polar body

the cell with little or almost no cytoplasm and will disintegrate

the secondary oocyte undergoes meiosis II to produce

two haploid cells: an ootid with bulk of cytoplasm and a second polar body

polar bodies

first may or may not divide - eventually all disintegrate with only one functional cell remaining

meiosis II is completed only after

fertilization