Biology- Cells Midterm

What is the nucleus?

Usually most conspicuous organelle. Contains most of the DNA in an eukaryotic cell. The information center, content inside has passage to cytoplasm through small passage called nuclear pores.

Nuclear membrane

Encloses nucleus and is a double membrane

Hereditary information

Encoded in DNA and reproduced in all body cells and passed to offspring

DNA program

Directs the development of biochemical, anatomical, physiological, and ( to some extent ) behavioural traits

Ribosomes

Use the information from the DNA to make proteins

Gene

The amino acid sequence of a polypeptide is programmed by a unit of inheritance called a gene. Genes are made up of DNA, a nucleus acid made of monomers called nucleotides.

what are the two types of nuclei acids

Deoxyribonucleic Acid ( DNA ) and Ribonucleic Acid ( RNA ).

What are the two roles of DNA

1. DNA provides directions for its own replication

2. DNA directs synthesis of messenger RNA (mRNA)and, through mRNA controls protein synthesis .

What is the central dogma

The central dogma of molecular genetics is that DNA makes RNA which makes proteins

Albinism

A mutation in a single gene causes major pehnotypic effect

What are the three major types of RNA does DNA make by transcription

1. mRNA - decoded message from gene/DNA - is translated

2. rRNA - structural component of ribosome - is not translated - key component of ribosome

3. tRNA - transports amino acids during translation - is not translated - key component of ribsome

What other 3 types of RNA are made but not major?

micro RNA, small RNA, RNA i

Who were James Watson and Francis Crick

Gave structure of DNA in 1953, won nobel prize in 1956

What did Watson and Crick propose

They proposed a double helix structure - two strands of DNA wrapped onto each other in a helical fashion

What are the components of Nucleic Acids

Nucleic acids are polymers called polynucleotides. Each polynucleotide is made of monomers called nucleotides. It has a sugar-phosphate backbone

nucleotide

nucleoside + phosphate group

nucleoside

nitrogenous base + sugar

Two types of nitrogenous bases

Pyrimidines and Purines

Pyrimidines

cytosine, thymine, uracil - single six membered ring

Purines

adenine, guanine - six membered ring fused to five membered ring ( double ring structure )

Sugars in DNA and RNA

In DNA, sugar is deoxyribose ( loses oxide )

In RNA, sugar is ribose ( has hydroxide )

5’ end

PO4

complimentary nature of DNA

2 strands compliment each other, certain molecules always bond to each other

Antiparallel nature of DNA

3’end and 5’end

3’ end

( OH )

Linking two nucleotides

Adjacent nucleotides are joined by covalent bonds formed between OH group and 3’ carbon of one nucleotide and phosphate on 5’ carbon on next

How are bases paired in DNA

hydrogen bonds

3 differences between RNA and DNA

1. RNA is single stranded

2. different sugars

3. RNA has uracil instead of thymine

The human karyotype

arrangement of paired chromosomes in decreasing order of length

Genome

All the DNA is a cell ( can consist of a single DNA molecule - common in prokaryotic cells, or a number of DNA molecules - common in eukaryotes cells )

Chromosomes

What DNA molecules in a cell are packaged into

Chromatin

Eukaryotic chromosomes consist of this, a complex of DNA and protein that condenses during cell division

Somatic Cells

non reproductive cells, have two sets of chromosomes (2n) body cells, 46 chromosomes

Gametes

reproductive cells, have half as many chromosomes as somatic cells ( n )

Cell Division

The continuity of life is based on the reproduction of cells or cell division

Unicellular organisms cell division

division of one cell reproduces the entire organism

Multicellular organisms cell division

Depend on cell division for:

1. developement from a fertilized cell

2. growth or organs and body cells

3. repair ex cut becomes closed

cell cycle

cell division is an integral part of the cell cycle, the life of a cell from formation to its own division

cell cycle consists of

mitotic phase (mitosis and cytokinesis)

interphase ( cell growth and copying of chromosomes in preparation for cell division) - G1, S(DNA synthesis), G2

eukaryotic cell cycle

1. G1 (gap phase 1 )

2. S (synthesis)

3. G2 ( gap phase 2)

4. M ( mitosis)

5. C (cytokinesis)

   The cell grows during all three phases but chromosomes are duplicated only during the S phase.

Eukaryotic cell division consists of

mitosis - the division of the nucleus

cytokinesis - the division of the cytoplasm

meiosis

gametes are produced by a variation of cell division called this. A special type of division produces nonidentical daughter cells (gametes, or sperm and egg cells ) It also yields non identical daughter cells that have only one set of chromosomes, half as many as the parent cell, the 4 daughter cells produced are different

Cyclins and Cyclin-dependant kinases

Two types of regulatory proteins involved in cell cycle control. The activity of a cyclin dependant kinase fluctuates during the cell cycle based on the concnetration of its cyclin partner, which controls cdk activity.

MPF

maturation promoting factor - is a cyclin-cdk complex that triggers a cells passage past the G2 checkpoint into M phase

centromere

the narrow waist of the duplicated chromosomes, where the two chromatids are most closely attached

Each duplicated chromosome has two ____ which seperate during cell division

sister chromatids

Mitosis

division of somatic cells, divided into four phases : prophase, metaphase, anaphase, telophase

G2 of interphase

chromosomes duplicated during S phase cannot be seen individually because they have not condensed

Prophase

The chromatin fibers become more tightly coiled, condensing . Nucleoli disappear, chromosomes pair up

mitotic spindle

forms during pro phase, composed of the centrosomes and the microtubules that extend

metaphase

centrosomes are now at opposite poles of the cell. Line up at the metaphase plate

anaphase

shortest stage of mitosis, separation of daughter chromosomes

telophase

chromosomes become less condensed, nucleoli reappear

cytokinesis

invloves formation of cleavge furrow or cell plate which pinches the cell into two

cleavage furrow

contractile ring of microfilaments

binary fission

prokaryotes reproduce by a type of cell division called this. In binary fission, the chromsome replicates (beginning at the origin of replication) and the two daughter chromosomes actively move apart

Asexual production

one parent produces genetically identical offspring by mitosis

clone

is a group of genetically identical individuals from the same parent

sexual production

two parents give rise to offspring that have unique combinations of genes inherited from the two parents(never be identical)

life cycle

the generation to generation sequence of stages in the reproductive history of an organism

sex chromosomes

the x and y

autosomes

the remainder 22 pairs of chromsomes

diploid cell

2n has two sets of chromsomes, 46 in humans

haploid cell

n found in gametes, 23

gamete (sperm or egg)

contains a single set of chromosomes, and is haploid

alternation of generations

means alternation of haploid and diploid state

How many chromosomes does each daughter cell have

has only half as many chromosomes as the parent cell

in meiosis 1

homologous chromosomes seperate, results in two halpoid daughter cells with replicated chromsomes, called reductional division,

meiosis 2

sister chromatids separate, results in four haploid daughter cells with unreplicated chromosomes, called the equational division, same as mitosis

Sinapsis

pairing of homologous chromosomes

Prophase 1

duplicated homologous chromosomes pair and exchange segments

Metaphase 1

chromosomes line up by homologous pairs

Anaphase 1

each pair of homologous chromosomes separate

telephase and cytokinesis 1

two haploid cells form, each chromosomes still consist of two sister chromatids

chiasmata

each tetrad usually has one or more chiasmata, x-shaped regions where crossing over occured.

tetrad

a group of 4 chromatids

Differences between mitosis and meiosis

1. mitosis conserves the number of chromosome sets, producing cells that are genetically identical to the parent cell

2. meiosis reduces the number of chromosomes sets from two (diploid) to one(haploid), producing cells that differ genetically from each other and from the parent cell

3. the mechanism for separating sister chromatids is virtually identical in meiosis 2 and mitosis

mutations

the original source of genetic diversity

alleles

mutations create different versions of genes

Three mechanisms contribute to genetic variation

1. independent assortment of chromosomes

2. crossing over

3. random fertilization

Independant assortmant of chromosomes

how they line up at equatorial pole

more than 8 million possible combinations of chromosomes

homologous pairs of chromosomes orient randomly at metaphase 1 of meiosis

crossing over

• crossing over produces recombinant chromosomes, which combine genes inherited from each parent

• in crossing over, homologous portions of two non sister chromatids trade places

• by combining dna from two parents into a single chromosome

random fertilization

• every sperm has a possibility to do this

replication

occurs in the nucleus of eukaryote, but cytoplasm of prokaryote

chromatin

(DNA and protein mix) is of 2 kinds (euchromatin and heterochromatin - junk DNA) and undergoes changes in packing during cell cycle

In a bacterium, dna is supercoiled and found where

nucleoid

eukaryotic chromosome shape

eukaryotic chromosomes are linear dna molecules associated with larger amount of protein

prokaryotic chromsoome shape

bacterial chromosomes is circular dna molecule associated with small amount of protein

euchromatin

loosely packed chromatin

heterochromatin

during interphase centromeres and tolomeres highly condensed into this

Watson and crick semi conservative model

predicts when double helix replicates, each daughter molecule will have one parental stand and one newly made strand. the two strands of the parental molecule separate, and each functions as template for synthesis of a new complementary strand

origins of replication

replication begins at particular sites called this, where the two dna strands are separated, opening up a replication “bubble”. replication proceeds in both directions from each origin, until the entire molecule is copied

dna polymerases

these enzymes catalyze the elongation of new dna at a replication fork , most of them require a primer and a dna template strand. Rate of elongation is about 500 nucleotides per second in bacteria and 50 per second in humans. can only add nucleotides to the 3’ end, cannot initiate synthesis of a polynucleotide

nucleoside triphosphate

each nucleotide that is added to a growing Dna strand

pyrophosphate

as each monomer of joins the dna strand, it loses two phosphate groups as a molecule of pyrophosphate

the initial nucleotide strand is a short ____

RNA primer

primase

this enzyme can start an RNA chain from scratch and adds RNA nucleotides one at a time using the parental DNA as a template. the primer is short (5-10 nucleotides long) and the 3’end serves as the starting point for the new DNA strand

okazaki fragments

the lagging strand is synthesized as a series of segments called this which are joined by DNA ligase

proteins

links between genotype and phenotype

process by which dna directs protein synthesis includes two stages

transcription and translation