Genetics Exam 1

Genetics

study of heredity, how inherited variation is encoded, replicated, and expressed, and how it evolves over time

Genomes

-the complete set of genetic instructions for any organism -all of these are encoded in nucleic acids (either DNA or RNA)

transmission genetics (classical genetics)

encompasses the basic principles of heredity and how traits are passed from one generation to the next

transmission genetics examples

relation between chromosomes and heredity, the arrangement of genes on chromosomes, and gene mapping

molecular genetics

chemical nature of the gene itself: how genetic information is encoded, replicated, and expressed

molecular genetics examples

cellular process of replication, transcription, and translation (by which genetic info is transferred from one molecule to another) and gene regulation (the processes that control the expression of genetic info)

population genetics

explores the genetic composition of populations (groups of individuals of the same species) and how that composition changes geographically and with the passage of time

population genetics examples

evolution

model genetic organism

organisms that are widely used in genetic research and that can serve as models for the genetic systems of other organisms

pangenesis

(incorrect) genetic info travels from different parts of the body to reproductive organisms

Inheritance of Aquired Characteristics (Lamarck)

(incorrect) acquired traits become incorporated into hereditary information.

Preformationism

(incorrect) minuture organism resides in sex cells and all traits are inherited from one parent

blending inheritance

-incorrect -genes blend and mix

germ-plasm theory

(correct) all cells contain a complete set of genetic information

cell theory

(correct) all life is composed of cells, and cells arise only from cells

Mendelian inheritance

correct; traits are inherited in accord with defined principles

gene

is the fundamental unit of heredity

Phenotypes are

physical expressions of genetic traits Ex. eye color

Chromosomes

a threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.

Mutations

Random errors in gene replication that lead to a change in the sequence of nucleotides. The source of all genetic diversity.

Evolution

Change in a kind of organism over time; process by which modern organisms have descended from ancient organisms.

Prokaryote

A unicellular organism that lacks a nucleus and membrane bound organelles

Eukaryotes

compartmentalized cell structure with components bounded by intercellular membranes(may be either unicellular or multicellular)

Nucleus

a nuclear membrane surround this, stores the genetic material

Histones

form tightly packed chromosomes (special class of stuff of eukaryotic chromosomes

Virusis

Smallest microorganisms known to cause infectious diseases

3 fundamental events cells have to do to reproduce successfully

1. its genetic information must be copied

2. the copies must be separated from each other

3. the cell must divide

binary fission

A form of asexual reproduction in single-celled organisms by which one cell divides into two cells of the same size

homologous pair

a pair of chromosomes, one from each parent, that have relatively similar structures and gene values

dipoid

(2n) a cell containing two sets of chromosomes inherited by each parent

Haploid

(genetics) an organism or cell having only one complete set of chromosomes

Polyploid

having three or more of each type of chromosome characteristic of the species

Centromere

Constricted region in a eukaryotic chromosome where sister chromatids are attached

Telomeres

stable ends of linear chromosomes

origin of replication

sites where DNA synthesis begins, unlike centromeres and telomeres, they are not easily observed by microscopy

sister chromatids

2 identical copies of the same chromosome that are held together at the centromere

condensins

bind to the DNA within chromosomes and bring about condensation, are a type of structural maintenance of chromosomes complex, also plays a role in chromosome segregation in bacteria

G0 phase

stable, non dividing period of variable length

Interphase

G1 phase, S phase, G2 phase

G1 phase

growth and development of the cell; G1/S checkpoint

S phase

The synthesis phase of the cell cycle; the portion of interphase during which DNA is replicated.

G2 phase

preparation for division; G2/M checkpoint

M phase

prophase, metaphase, anaphase, telophase

Prophase

chromosomes condense and mitotic spindle forms

Prometaphase

nuclear membrane disintegrates and spindle microtubules anchor to kinetochores.

Anaphase

sister chromatids separate, becoming individual chromosomes that migrate toward spindle poles

Metaphase

chromosomes align on the metaphase plate; spindle - assembly checkpoint

Telophase

chromosomes arrive at spindle poles, the nuclear membrane re-forms and the condensed chromosomes relax

Cytokinesis

the cytoplasmic division of a cell at the end of mitosis or meiosis, bringing about the separation into two daughter cells.

crossing over

takes place in prophase 1, refers to the exchange of genetic material between non-sister chromatids (chromatids from different homologous chromosomes

Recombination

the creation of new combinations of alleles on a chromatid

Prophase 1

Chromosomes condense, homologous chromosomes synapse, crossing over takes place, nuclear envelope breaks down, and mitotic spindle forms.

Metaphase 1

homologous chromosomes line up in the middle of the cell

Anaphase 1

the two chromosomes (each with two chromatids) of a homologous pair separate and move toward opposite poles

Telophase 1

chromosomes arrive at the spindle poles

prophase 2

chromosomes condense, the spindle forms, and the nuclear membrane disintegrates

metaphase 2

individual chromosomes line up on the metaphase plate

Anaphase 2

sister chromatids separate and move as individual chromosomes toward opposite spindle poles

telophase 2

• the chromosomes arrive at opposite poles

• nuclei form around each set and the chromosomes unwind -the spindle breaks down and a nuclear envelope re-forms

cohesion

a protein that holds chromatids together, is key to the behavior of chromosomes in mitosis and meiosis

Spermatogenesis

Formation of sperm

spermatogonia

a cell produced at an early stage in the formation of spermatozoa, formed in the wall of a seminiferous tubule and giving rise by mitosis to spermatocytes.

spermatids

four haploid cells that are formed when a diploid reproductive cell divides meiotically

Oogenesis

the production, growth, and maturation of an egg, or ovum

1st polar body

the cell may or may not divide further

second polar body

a small body containing the chromosomes discarded during the second meiotic division of an ovum

super coiling of DNA

takes place when the DNA helix is subjected to strain by being overwound or under wound

relaxed state

a stretch of 100 bp of DNA would assume about 10 complete turns

positive super coiling

molecules that are over rotated exhibit this

negative super coiling

under rotated molecules exhibit this

topoisomerase

corrects "overwinding" ahead of replication forks by breaking, swiveling, and rejoining DNA strands

Nucleoid

confined to a definite region of the cystoplasm, its DNA frequently appears as a distinct clump

Chromatin

The complex of DNA and proteins that makes up eukaryotic chromosomes. When the cell is not dividing, chromatin exists in its dispersed form, as a mass of very long, thin fibers that are not visible with a light microscope

Euchromatin

undergoes the normal process of condensation and de-condensation in the cell cycle

Heterochromatin

Eukaryotic chromatin that remains highly compacted during interphase and is generally not transcribed.

nonhistone chromosomal proteins

chromatin constituents other than histones with a wide variety of functions. Human chromosomes associate with several thousand different kinds of nonhistone proteins.

Nucleosome

repeating subunit of chromatin fibers, consisting of DNA coiled around histones

topologically associated domains (TADs)

Large regions of spatially interacting chromatin; help to control gene expression in eukaryotic cells.

polytene chromosomes

Giant chromosomes

• arise when repeated rounds of DNA replication take place without accompanying cell divisions, producing thousands of copies of DNA that lie side by side

chromosome puffs

Localized swelling of a polytene chromosome; a region of chromatin in which DNA has unwound and is undergoing transcription.

epigenetic changes

Changes to the chemical groups that associate with DNA that are transmitted to daughter cells after cell division

telomeric sequences

usually consist of repeated units of a series of adenine or thymine nucleotides followed by several guanine nucleotides, taking the forms 5'-(A and T)m Gn-3' where m ranges from1-4 and n is 2 or more

Shelterin

A multiprotein complex that binds to mammalian telomeres and protects the ends of the DNA from being inadvertently repaired as a double-stranded break in the DNA.

C-value

the total amount of DNA in the haploid genome of a species

Denaturation

In proteins, a process in which a protein unravels and loses its native conformation, thereby becoming biologically inactive. In DNA, the separation of the two strands of the double helix.

renaturation

denaturation of DNA by heating is reversible; hydrogen bonds will form again between complementary base pairs, producing double-stranded DNA

Hybridization

Breeding technique that involves crossing dissimilar individuals to bring together the best traits of both organisms

endosymbiotic theory

proposes the mitochondria and chloroplasts were once free-living bacteria that became internal inhabitants (endosymbionts) of early eukaryotic cells

Heteroplasmy

Presence of two or more distinct variants of DNA within the cytoplasm of a single cell. (meaning that the gene is not just homozygote recessive or dominate in the F1 generation)

replicative segregation

Random segregation of organelles into progeny cells in cell division. If two or more versions of an organelle are present in the original cell, chance determines the proportion of each type that will segregate into each progeny cell.

homoplasmy vs heteroplasmy

Mitochondria within a cell can all have the same (identical) mtDNA (homoplasmy) or 2 or more mitochondrial genomes (heteroplasmy)

Mitochondrial Replacement Therapy (MRT)

those methods combine the nuclear DNA of a female who carries a mitochondrial mutation with that of a sperm and the egg cytoplasm of a healthy donor, creating a "3-parent" baby

Gene

an inherited factor (encoded in the DNA)

Allele

one of 2 more alternative forms of a gene

locus

a specific place on a chromosome occupied by an allele

Genotype

a set of alleles possessed by an individual organism

Homozygote

An individual organism possessing two of the same alleles at a locus

Heterozygous

an individual organism possessing 2 different alleles at a locus

characteristic or character

an attribute or feature possessed by an organism

Phenotype or trait

the appearance or manifestation of a characteristic