genetics and the organism

heredity

the passing of traits from parent to offspring.

The domestication (ie. “improvement”) of plants and animals

Man-made or artificial selection shows that man has made use of basic evolutionary principles for many millennia through the process of selective breeding or propagation.

Genetics

formal, scientific or quantifiable study of heredity (inheritance of genes, alleles, traits and genetic diseases).

What plants were domesticated in East Africa?

Barley, coffee, cotton, and wheat.

What animals were domesticated in East Africa?

Ass and dromedary.

What plants were domesticated in West Africa?

Gourds, melons, rice, and yams.

What animal was domesticated in West Africa?

Pig

What plants were domesticated in Southwest Asia?

Beets, carrots, grapes, melons, onions, and wheat.

What animals were domesticated in Southwest Asia?

Bactrian camel, cattle, dog, goat, horse, and sheep.

What plants were domesticated in Southeast Asia?

Bananas, cucumbers, lettuce, rice, sugar cane, tea, and yams.

What animals were domesticated in Southeast Asia?

Chicken, dog, duck, goose, pig, water buffalo, and zebu cattle.

What plants were domesticated in North Central China?

Apricots, barley, cabbage, peaches, plums, and soybean.

What plants were domesticated in the Mediterranean region?

Celery, dates, garlic, grapes, lettuce, and olives.

What animals were domesticated in the Mediterranean region?

Goat and cattle.

What plants were domesticated in North America?

Artichoke, blueberry, cranberry, sunflower, and tobacco.

What plants were domesticated in Meso-America?

Beans, chili pepper, cotton, maize (corn), squash, and sweet potato.

What animals were domesticated in Meso-America?

Dog and turkey.

What plants were domesticated in Western South America?

Papaya, potato, pumpkin, and tomato.

What animals were domesticated in Western South America?

Alpaca, guinea pig, and llama.

What plants were domesticated in Eastern Brazil?

Beans, Brazil nuts, cacao, pineapple, rubber, and tobacco.

Gene

fundamental functional unit of our DNA

DNA

deoxyribonucleic acid, carrier of our genetic information

Alleles

variants of a particular gene

Genetic information

carried by a four letter code consisting of 4 different nucleotides: A, G, C, T

nucleotide

structural unit of DNA

Nucleotide consists of three components:

deoxyribose sugar, phosphate group (PO4-), and nucleotide base

purines

adenine and guanine double ring structures

pyrimidines

cytosine and thymine single ring

codon

A series of any three of the four nucleotides which codes for a particular amino acid

Genetic code

3 letter codon made from the 4 letter alphabet, A, G, C, T (64 possibilities code for 20 amino acids)

Ribose vs. Deoxyribose

Ribose has an -OH attached to the

2’ carbon atom while Deoxyribose

has an -H atom.

A’s and T’s base-pair

2 hydrogen bonds

G’s and C’s base-pair

3 hydrogen bonds

Double-stranded DNA

consists of two anti-parallel polynucleotide strands of DNA that are base-paired with each other with hydrogen bonds, two hydrogen bonds between A’s and T’s, and 3 hydrogen bonds between G’s and C’s.

DNA polymerase

uses base-pairing rules to attach the phosphate of each new nucleotide to the 3’ OH group of the last nucleotide of a growing polynucleotide strand, creating a 5’ to 3’ polarized daughter strand of DNA that is complementarily base-paired with the parent DNA strand in an anti-parallel direction.

Structure of DNA

Double helix formed from two anti-parallel polynucleotide strands of deoxyribonucleotide-phosphates linked together with hydrogen bonds between specific purine-pyrimidine base-pairs.

DNA molecule diameter

2.0nm

Each turn of the B form of DNA is

3.4nm

Each nucleotide base-pair has a spacing of

0.34 nm

Therefore, there are how many base pairs for each turn

10 base pairs

asymmetric groove pattern

larger major groove and a smaller minor groove.

DNA

usually associated with structural proteins that help the cell organize the DNA, regulate the expression of genes, and protect the DNA from endogenous nuclease digestion, and from exogenous reactive oxygen species (ROSs).

What is the usual state of DNA in a cell?

DNA is usually in an uncondensed state called chromatin.

Is uncondensed chromatin easily visible with a light microscope?

No, it is not readily visible.

When does chromatin become visible under a light microscope?

When it becomes partially condensed as heterochromatin or fully condensed during mitosis.

What is heterochromatin?

A partially condensed form of chromatin that appears as dark-staining spots.

What type of dyes stain heterochromatin?

Basophilic dyes.

What does heterochromatin look like when stained?

It appears as dark-staining spots.

What does a small dark spot near the nuclear membrane represent in females?

The condensed, inactivated X chromosome.

When does X-chromosome inactivation occur?

During the morula stage, at approximately the 32-cell stage of embryonic development.

How does heterochromatin appear under an electron microscope?

It appears electron-dense.

What happens to chromosomes at the beginning of mitosis?

They condense and become visible under a microscope.

How many pairs of chromosomes make up the human genome?

23 pairs.

How do human chromosomes vary?

They vary in length, centromere position, and banding pattern.

How are the first 22 pairs of human chromosomes numbered?

In order of length, from chromosome 1 to chromosome 22.

What are the 23rd pair of chromosomes called?

the sex chromosomes

What are the typical sex chromosomes in females?

Two X chromosomes, or XX.

What are the typical sex chromosomes in males?

One X chromosome and one Y chromosome, or XY.

Karyotype

orderly display of chromosomes prepared from a sample containing metaphase cells, stained with a basophilic dye (eg. Giemsa), and arranged in pairs on the basis of size.

Cytogenetics

study of chromosome number, structure and banding pattern.

p arm

short arm

q arm

longer arm

centromere

constricted area where the sister chromatids are attached

sister chromatids

product of semiconservative DNA replication

Telomere

tips of each sister chromatid

G1

chromosomes are singlet

S phase

sister chromatids form upon completion of DNA replication/DNA synthesis

G2

duplex chromosomes consist of two sister chromatids

Prophase

chromosomes begin to condense

Metaphase

chromosomes moved to the equator

Anaphase

46 sister chromatids separate into 92 daughter chromosomes

Telophase

92 daughter chromosomes separate into 2 sets of 46

Cytokinesis

cell division

The DNA sequences of the great apes and man

differ by less than 2%.

locus

Staining a chromosome with Giemsa stain, naming the chromosome first,

followed by the arm, followed by the band and subband.

Locus for the mutation of gene ATP7A

that is responsible Menkes Disease: Xq13.3 [X chromosome, long arm (q),

band 1, sub-band 3.3]

How long is the haploid human genome?

About 3.2 billion base pairs.

How many genes does the haploid human genome contain?

Approximately 22,000–23,000 genes.

How many polypeptides does the human genome code for?

Close to 80,000 polypeptides.

What is the linear length of the haploid human genome

About 1 meter.

How much DNA is found in each diploid human somatic cell?

About 2 meters of DNA.

How is DNA packed inside the nucleus?

It is tightly coiled into chromatin.

What is the approximate diameter of the nucleus in a human cell?

About 6 μm, or 0.006 mm.

What is the smallest object visible to the unaided eye?

Approximately 80 μm, or 0.08 mm.

What is a gene locus?

The specific location of a gene on a chromosome

How is a gene locus named?

By chromosome number, chromosome arm, band number, and sub-band number.

What is the gene locus designation for the mutation causing Hemophilia A?

Xq28

What does the locus designation Xq28 mean?

The gene is on the long arm of the X chromosome, at band 28.

What normal gene is affected in Hemophilia A?

The gene that codes for clotting factor VIII.

What is the function of clotting factor VIII?

It helps form blood clots when a blood vessel is damaged.

genetic trait

observable property of an organism that results from the expression of a gene that codes for a protein that produces that trait.

What type of traits are controlled by a single copy of a gene?

Dominant traits.

What type of traits are expressed only when two alleles are present?

recessive trait

What are polygenic traits?

Traits controlled by interactions between multiple genes.

What is an example of a polygenic trait?

Eye color.

What are multifactorial traits?

Traits influenced by multiple genes and environmental factors.

What are examples of multifactorial traits?

Skin color and height.

How are most human traits determined?

By the interaction of multiple genes, often combined with environmental factors.

1865 Gregor Mendel

an Augustinian monk worked with the garden pea plant to

establish the foundations of modern genetics.

Factors that determine traits

passed from parent to offspring.