Chapter 1 Flashcards
Genetics
The study of the general mechanisms of heredity and the variation of inherited traits.
Genomics
-The study of the function of all the nucleotide sequences present within the entire genome of a species, including genes in deoxyribonucleic acid (DNA) coding regions and in the DNA noncoding regions.
-Genomics includes genetics, but has a broader scope
Gene
-Specific set of instructions cells use to produce a specific protein.
-Some genes tell each cell what protein to make and how to make it
-Other genes control a cell’s protein- making activity by determining when to make a specific protein and how much to make.
-Thus, a gene acts as a specific “recipe” for making a protein.
Most genes are part of the DNA in the nucleus of body cells. Figure I - I shows a cell nucleus with DNA in the form of chromosomes. Figure 1-2 depicts an enlarged chromosome to show that a chromosome is composed of DNA and contains segments that are genes.
Genome
-The complete set of genes for out species
-All human cells with a nucleus contain rwo sets of every gene that humans possess
-Contains between 20,000 and 25,000 individual genes
-(Mature germ cells-sperm and ova-contain only one set of every human gene.)
Gene expression
-The activation of a gene allowing its product to be made by the cell is called gene expression
- (Ex. all nucleated cells contain all the human genes, however no single cell type produces all the proteins coded for by these genes—For example, only the thyroid gland normally produces thyroid hormones, even though all cells have the genes for thyroid hormones. Although genes for thyroid hormones are present in all cells, they are SELECTIVELY ACTIVATED and expressed exclusively in the thyroid gland, resulting in the production of thyroid hormones)
-In all other cell types, REGULATOR GENES prevent the structural genes for thyroid hormones from being expressed.
Proteome
-The complete set of all proteins that a person makes at a given time under certain conditions.
-Proteomes can be examined for one cell type or for an entire organism.
-(ex. The protein estrogen is part of the proteome for ovarian cells but is not part of the cardiac muscle cell (myocardial cell) proteome. When considering the entire human proteome, we are looking at the proteins produced by all the individual cellular proteomes.)
Proteomics
The study of how proteins found in the proteome interact with each other
Chromosome
-A temporary but consistent state of condensed DNA structure formed for the purpose of cell division
-Although DNA appears different from a gene and from a chromosome, they are all the same substance. DNA is the basic genetic chemical structure, containing gene-coding regions and noncoding regions, which can be compressed into a chromosome form.
-Genes and chromosomes are both composed of DNA.
-[Ex. Consider a sweater as a chromosome and each separate part of the sweater (right sleeve, left sleeve, pocket, collar, front, and back) as a gene. Now consider that the entire sweater (chromosome) and its parts (genes) are composed of yarn (DNA). A sweater is not a person’s entire wardrobe, however, just like one chromosome and all the genes it contains are not the entire genome. Think of the genome as being the entire wardrobe (all the person’s shoes, socks, underpants, pants, shirts, etc). Each chromosome has many genes within it. Larger chromosomes contain thousands of genes, and smaller chromosomes may have fewer than 100 genes.]
Gene locus
-The specific chromosome locations of a gene
-For example, the insulin gene’s locus is llq 13, which means that the gene is located on the long arm of chromosome 11 in region 13 (Fig. 1-3).
-[Ex. When it is time to make more insulin, this is the “page” where the recipe can be found, Although all cells have the “recipe” for insulin on chromosome 11, it is only opened and read by the beta cells of the pancreas. Other cells normally cannot “read” the insulin recipe and do not make insulin.]
[DNA structure]
Bases
-The basic structure of DNA is a set of four nucleic acids.
-These nucleic acids are nitrogen-containing compounds.
-These four bases are adenine (A), cytosine (C), guanine (G), and thymine (T)
[DNA structure]
Pyrimidines
Single-ring structure
Thymine and cytosine
[DNA structure]
Purines
Adenine and Guanine
Double-ring structures
[DNA structure]
Nucleoside
Nucleotide
-Each base becomes a nucleoside when a five-sided sugar (known as a deoxyribose sugar) is attached to it
(see Fig. 1-4).
-Each nucleoside becomes a complete nucleotide when a phosphate group is attached
-The nucleotide is the final form of a base that is placed into the DNA strand.
-The nucleotides within each strand are held in position by the linked phosphate groups, which act like the string holding beads together to form a necklace.
[DNA Structure]
Base Pairs
Base pairs are the complementary bases in the two strands of DNA.
-These DNA strands must remain perfectly parallel to each other, and the pairings of the nucleotides make this happen.
-For double-stranded DNA (dsDNA) to remain parallel, the two strands must stay the same distance apart down the total length of DNA.
[DNA structure]
Complementary pairs
-A pyrimidine with a single-ring Structure always pairs up with a purine that has a double-ring structure to maintain this proper distance
-AT, CG
-DNA strands held together loosely by weak H bonds
-These weak bonds allow the two strands to separate easily during cell division when the DNA is to replicate.
-This separation does not require a 10[of energy and can occur quickly.
- Adenine and thymine each have a site for two hydrogen bonds to form, whereas cytosine and guanine each have three sites for hydrogen bonds to form (see Fig. 1-4).
[DNA structure]
-Except during cell division. the two parallel strands of DNA are twisted into a loose helical shape (see Figs. 1-2 and 1-5).
-The DNA supercoils tightly into the chromosome shape (which is visible with standard microscopes) only when a cell undergoes mitosis.
-Each nucleus contains much more DNA than is needed for the 20,000 to 25,000 genes. The gene part of the DNA is only about 5% of all the total DNA in each cell’s nucleus, with the remaining DNA (called noncoding DNA) playing various roles in regulating gene expression.
DNA replication
-Every time a cell divides, DNA replication occurs, which is duplication or reproduccion of itself, resulting in two identical sets of DNA.
-This is needed because every time a cell undergoes MITOSIS, a duplicacion division results in two new cells that are idencical both to each other and to the original cell (parent cell) that began the mitosis, and each cell must have a complete genome.
[DNA replication]
Mitosis
- Duplication division which results in two new cells that are idencical both to each other and to the original cell (parent cell) that began the mitosis
-Each cell must have a complete genome.
-Mitosis occurs in a regulated pattern known as the cell cycle.
-To undergo mitosis, a cell first must be a cell type capable of cell division. [Some cells do nor divide once organ maturation is complete. Examples of these nondividing cells include skeletal muscle cells, cardiac muscle cells, and neurons.] - If a cell has retained the ability to divide when needed ,it will respond to signals to leave G0 and enter the cell cycle
[Cell division]
Cell cycle
-Regulates mitosis
-Cells not actively dividing are in a reproduccive resting state known as G0- In this state, the cell is accively performing its specific funccions but is not reproducing.
-[ex. example, skin cells in the Go state produce keratin and other skin products but do not reproduce.]
-Normal cells are in the state of Go most of the time and leave it only to reproduce when generacion of more cells is needed.
-The cell cycle involves four phases.
-Movement through these phases for successful generation of two new cells requires selective gene input (promitosis genes).
[DNA synthesis]
The process of manufacturing DNA,
DNA synthesis vs DNA replication
DNA synthesis is the process of manufacturing DNA, whereas DNA replication is synthesis resulting in two identical strands-an original and a replica, or copy.
Cell Cycle Phase Table
-Cells not actively dividing are in a reproduccive resting state known as G0
- In this state, the cell is accively performing its specific functions but is not reproducing.
-Generating two new cells from one parent cell requires twice the DNA present in the parent cell.
-Notice in Figure 1-7 that the nucleus during S phase is twice as large as it was during G1 because it now has twice as much DNA.
-This replication of the DNA ensures that the two new cells resulting from mitosis will each have the same amount of DNA as the parent cell.
-The parent cell doubles its DNA content by DNA replication in S phase. (Memory hint: S phase stands for synthesis of DNA.)
DNA replication
-DNA replication begins when the individual sets of dsDNA separate by breaking the hydrogen bonds holding the two strands in the double-helix form
- Once they separate, enzymes at each end of the strands read the sequence of the original strands and build two new strands that are complementary to the original strands.
-DNA read from 5’ to 3’ end (these numbers refer to the specific carbon on the sugar molecule that connects with the phosphorous molecule).
-Because new bases can only be added at the 3’ end, building or reading from 5’ to 3’ is termed downstream, and reading from 3’ to 5’ is termed upstream.
-Because each of the two new sets of dsDNA contains one of the original strand, this type of DNA synthesis is known as the semiconseruatiue model of DNA replication.
Enzymes participating in DNA replication
Table 1-2
Histones
Figure 1-10
- set of globular protein balls
- DNA supercoiling occurs in organized steps.
- Initially, dsDNA coils up tightly.
- It wraps around histone protein balls (histones).
- This compacts DNA without damage.
- DNA-wrapped histones cluster into nucleosomes.
- Nucleosomes form thicker “beaded”groups.
- These groups coil into a dense solenoid, which is a dense, compressed supercoil and loop.
- Chromosomes’ basic structure is formed.
- Compact structure condenses millions of base pairs.
- Dense chromosomes can be stained for visualization.
Chromosome
-As shown in Figure 1-10, a chromosome is a specific large chunk of dsDNA that has already undergone DNA replication and contains millions of bases and hundreds (sometimes thousands) of genes.
-During M phase (metaphase of mitosis), each chromosome forms and moves to the center of the cell that is about to divide.
-Just before the cell splits into two cells {cytokinesis}, each chromosome is pulled apart (nucleokinesis) so that half of each duplicated chromosome goes into one new cell, and the other half goes into the other new cell.
-This action is illustrated in Figure 1-11, showing just 2 chromosomes rather than 46.
[Chromosome Structure]
Ploidy
The actual number of chromosomes present in a single-cell nucleus at mitosis.
the number of sets of chromosomes in a cell, or in the cells of an organism.
[Chromosome Structure]
Haploid chromosome number (1N)
Diploid chromosome number (2N)
-Humans have 46 chromosomes divided into 23 pairs.
-A complete set of one of each chromosome is the haploid chromosome number (1N) representing 23 individual chromosomes.
-When the nucleus contains both pairs of all chromosomes, the number present is the diploid chromosome number (2N).
