Bio Exam #2 Studying

Genome

all genetic material of an organism that is transmitted from parent to offspring

Sequence of a genome

sequence of all nucleotides along the DNA molecules in a cell

Histones

proteins that help compact DNA into small space of nucleus.

Chromatin

the resulting DNA protein complex that occupies a much smaller volume than DNA alone.

Chromatin needs to be…

tightly paced to fit into the nucleus and also so it can be equally divided into two daughter cells when cells are replicated

Uncoiled DNA is….

hard to separate

Coiled DNA is….

easier to separate and forms when the cell is getting ready to divide.

Compact DNA is called…

chromosomes

DNA is uncoiled…

most of the time and turns into chromosomes in preparation for division

Unreplicated Chromosomes have….

single, long DNA double helix wrapped around proteins (which are too small to distinguish at this scale).

Replicated chromosomes has…

two copies of the same DNA double helix.

Condensed repliacted chromosome consist of…

DNA condensed around its associated proteins, resulting in a compact chromosome that is 10,000 times shorter than its original length

Gene is the…

basic unit of inheritance

Gene is the region…

of DNA in a chromosome that codes for a particular protein (or RNA)

Genes occupy…

specific positions on chromosomes

Locus…

the physical site or location of a gene on a chromosome

A given gene is always found in the same position (locus) on both of the….

chromosomes in a homologous pair

Allele…

one of two or more alternative forms of a gene that are found at the same locus.

Homologous pair…

a set of two matching chromosomes

Different versions of the same gene are still both genes that code for something but…

can code for different things

Homozygous…

same allele for a gene

Heterozygous…

different alleles of a gene

Amount of genes in a genome…

varies from species to species

Size of genome does not relate….

to the size/complexity of the organisms. For example humans have 22k while a plant has 27k. More does not always mean more complex. SAME GOES FOR CHROMOSOMES

Somatic cells…

non reproductive cells

Each human chromosomes contains…

hundreds to thousands of genes

A base pair is…

a nucleotide in the DNA double - helix, and its complementary nucleotide.

Telomeres….

are ends of chromosomes

Centromere…

are centers of chromosomes

In preparation for cell division, chromosomes….

replicate

Each chromosomes is…

identical and an exact copy of one another

Chromatids…

chromosomes that are held together after DNA replication, and they are sister chromatids as they are direct copies of one another and are held together by proteins.

Two sister chromatids are…

still only one chromosome as they are identical to one another

During cell division, each daughter cell gets…

one of the copies that were made during DNA replication and each new daughter cell still has one chromosome

Each daughter cell has…

a copy of the DNA that was repliacted

As long as sister DNA was held together at their center by proteins…

they are still considered to be one chromosome

Cell division…

is the process by which a single cell becomes two daughter cells

Asexual reproduction…

2 identical daughter cells are produced

aSexual Reproduction…

offspring receive genetic material from 2 parents

Meiosis leads…

to the production of sperm and eggs.

Gametes…

are the specialized cells that contain each parent’s genome.

Meiosis and mitosis are usually accompanied by….

cytokinesis

Cytokinesis…

the division of cytoplasm into two distinct cells.

Meiosis…

cell division that reduces the number of chromes by half to produce gametes. Takes diploid cell and turns into haploid cell.

Mitosis…

process of cell division where a single parent cell duplicates its genetic material and divides to produce two genetically identical daugher cells

Diploid….

cells containing two complete sets of chromosomes/2 copies of each chromosome . (HOMOLOGOUS CHROMOSOMES)

two copies of each chromsomes (one from each parent)

created and maintained through mitosis

make up body tissue

Human example- all our cells contain 23x2 chromosomes (46) EXCEPT our reproductive cells. 

Haploid…

cells containing only a single set of unpaired chromosomes

only one copy of each chromosome type

created through meiosis

exclusively for reproduction

Human example - our reproductive cells (Gametes) only contain 23 chromosomes.

How do cells replicate?

1. DNA is copied

2. The copies are separated

3. The cytoplasm is divided to create two complete cells

G1…

most cells found in this stage

cellular content, excluding the chromosomes are duplicated

S phase…

synthesis (DNA replication)

prepares for cell division and the genome has to be replicated

DNA/chromosomes begin to be replicated

each of the 46 chromosomes is duplicated by the cell

G2….

double check duplicated chromosomes for error, making any needed repairs

M phase…

mitosis happens which is cell division and cytokinesis.

G0 phase…

cells spend time in this phase and they rest/ a break phase

not actively dividing or preparing to divide.

G1, S, and G2 together are rendered to as….

interphase.. which is where most cells spend time and they are transcribing, translating, etc.

Cells replicated DNA so that even after cell divans, the daughter cells are…

still left with a full genome.

PLOIDY…

the number of sets of chromosomes in a cell

Polyploid…

cell contains more than 2 copies of each chromosome (usually plants).

We are diploid because…

gametes fuse and the result is the cells that are diploid and have 2 sets of 23 chromosomes for a total of 46.

A human gamete contains one set of…

23 chromosomes…so it is a haploid genome…indicated with n (or, 1n) -23

In fertilization, 2 (haploid) gametes…

fuse

The result is a….

diploid cell, contains two sets of 23 chromosomes

We indicate diploid genome with…

2n=46

Chromosomes are….

in pairs (homologous chromosomes)

Human genome….

representation of identical human diploid karyotype, showing the organization of the genome into 23 pairs of homologous chromosomes.

Chromosomes are shown….

aligned at their centromeres

Chromosomes 1-22…

autosomes

Chromosome 23:

sex chromosomes

The member of each pair are called…

homologous chromosomes and were inherited, one from mother and one from father.

Unreplicated Chromosome…

a chromosome that consists of one double-helical molecule of DNA packaged with proteins for compactness

Replicated chromosome…

a chromosome after DNA replication. Consists of 2 identical chromatids, each containing one double-helical DNA molecule packed with proteins for compactness.

Sister chromatids…

The 2 identical chromatid copies in a replicated chromosome

Homologous Chromosomes (homologs)

Chromosomes that have the same gene in the same position and are the same size and shape. (because the alleles of particular genes are often different between the homologs, homologs are not called identical chromosomes).

Non-sister chromatids…

Chromatids on different members of a homologous chromosome pair. (To be non-sister chromatids, one of the chromatids is on one homolog and the other chromatic is on the other homolog).

Homologous…

not identical and can have different versions of the genes

Sister chromatids are all on one…

chromosome

DNA replication produces…

an identical copy of the double-stranded DNA that makes up the chromosome

Two copies of DNA are…

genetically identical

Each “half” of this compact is an individual DNA molecule called…

a chromatid

As long as the two sister chromatids resulting from replication are joined at their centromeres, this is still considered a…

single chromosome

The two sister chromatids will only be separated from each other during…

cell division

Chromatids separate during…

cell division

Outcomes of DNA replication…

replication doubles the amount of DNA, but not the number of chromosomes

After DNA replication…

the cell has the same number of chromosomes, but each replicated chromosome is now made of two attached identical sister chromatids

We only increase the number of DNA not the number of…

chromosomes during replication

After replication, we have sister chromatids and they are still…

each one individual chromosome

Chromosomes must be copied (replicated) before…

cell division

DNA molecules are copied in the process of…

replication

Replication…

sequence of DNA allows it to specify exact copies of itself COPYING MUST BE EXACT

Mutation…

error in DNA replication

Semiconservative model of replication…

Every new DNA strand will have one parental strand and one new strand

Semiconservative replication produces…

daughter molecules with both an original and a newly synthesized DNA strand

DNA polymerase replicated DNA by synthesizing a new strand…

5’ to 3’

DNA is double-stranded and must be unwound and rewound in small sections to allow for…

replication (a replication fork is formed)

Each strand of DNA is copied in a…

semiconservative replication, forming two double-stranded molecules with one new strand and one old stand each.

If DNA is always made in the 5’ to 3’ direction, one strand would run out of template and get caught in the rewinding double-helix so to avoid this…

strands are synthesized differently

Leading strand is made in a straightforward way with the daughter strand growing along in the…

same direction as the replication fork

Step 1, DNA is locally unwound by…

an enzyme called Helicase

Step 2, RNA primate adds a…

primer so that there is a free 3’ OH to join onto

Step 3, Synthesis of the…

leading strand (via DNA polymerase) begins (5’ to 3’)

On the other strand, lagging strand, DNA is…

synthesized in small chunks that are eventually linked together.