Bio Keystones

6 reasons - Why must cells divide?

To Grow

To Develop

To Heal injuries

To replace dead cells

To reproduce

To maintain a small size

Cancer

Why do cells limit their size?

To prevent stress on DNA

Difficulty moving nutrients/wastes across membrane

Ratio of surface area to volume

Cell membrane = surface area

Cytoplasm = volume

Volume increases at a faster rate than surface area

What size cell would be the most efficient

2

Before a cell becomes too large, it divides, producing...

2 daughter cells: Each daughter cell has SAME DNA as parent cell

What are chromosomes?

Structure within the nucleus containing the (DNA) that is passed from one generation of cells to the next

1 chromosome equals?

1 strand DNA

Chromatin

visible within the nucleus; consists of DNA and histone proteins

What are unreplicated chromosomes?

1 strand of DNA.

Looks like an "I"

What are Replicated Chromosome:

2 strands of IDENTICAL DNA.

Joined in center.

Looks like an "X"

What are Chromatid?

one of two identical "sister" parts of a duplicated chromosome

What is a centromere?

an area where the chromatids are attached to one another

What are the 2 stages of cell division? (eukaryotes)

Mitosis- division of the cell nucleus

Cytokinesis- division of the cytoplasm

What are the 2 stages of cell division known for ?

Known as Asexual reproduction

unicellular organisms & prokaryotes

Ex. bacteria - binary fission

What are the two major phases of the cell cycle?

Interphase

(GROWTH)

Mitosis

(DIVISION)

What are the sub 3 phases of inerphase?

G1

S

G2

What happens in G1?

cell grows

What happens in the S phase?

DNA is "synthesized"

Start with 1 strand of each DNA. End with 2 identical copies of each DNA

What happens in the G2 phase?

Checkpoint and more cell development

What are the 4 phases of mitosis?

prophase, metaphase, anaphase, telophase (Followed by Cytokinesis)

What happens in prophase of mitosis?

Nucleolus disappears

Nuclear envelope breaks down

Chromosomes become visible

Chromosomes become attached to spindle fibers at centromere

What happens in metaphase of mitosis?

Chromosomes line up across the cell equator

Spindle Fibers connect the centromere of each chromosome to the two poles of the cell

What happens in anaphase of mitosis?

Spindle fibers pull replicated chromosomes apart

Centromeres split

Unreplicated chromosomes separate and move to opposite poles of the cell

What happens in telophase of mitosis?

Chromosomes begin to unwind back into chromatin

Nuclear envelope re-forms

Spindle begins to break apart

Nucleolus becomes visible

(Happens at same time as Cytokinesis)

What happens in cytokinesis of mitosis?

Occurs at the same time as Telophase

Division of the Cytoplasm

Result? 2 new identical cells

Different in Plant and Animal Cells

What is the difference between cytokineses in plant and animal cells?

Animal cells:

Cell membrane pinches inward until the cytoplasm is split into 2 new cells

Indentation is called cleavage furrow.

Plant cells:

Cell plate forms midway between the divided nuclei

Cell wall begins to appear in the cell plate

What are cyclins?

proteins that regulate when cells divide.

What are internal regulators?

respond to things in the cell

i.e. make sure all chromosomes have been replicated

What are external regulators?

respond to events outside the cell

i.e. Wound healing

What is cancer?

when cells lose control over growth

Cancer cells do not respond to the signals that regulate the growth of most cells

What is the p53 gene?

halts the cell cycle until all chromosomes have been properly replicated

What is meiosis?

The form of cell division by which GAMETES, with HALF the number of CHROMOSOMES, are produced.

What are gametes?

sex cells (sperm and egg)

What do homologous pairs contain?

Homologous pairs contain DNA that codes for the same genes , but different versions of those genes

When do Homologous pairs cross over?

Prophase 1

What are the three parts of a Nucleotide?

phosphate group, sugar, nitrogenous base

What two parts of the nucleotide make up the backbone of the molecule?

Sugar, Phosphate

DNA is made up of what?

Made of repeating nucleotides (subunits of nucleic acids)

Sugar-phosphate backbone with hydrogen bonds weakly attaching nitrogen bases (ACTG)

What is the complementary strand:

ACTTAACCGGATTCCATG

TGAATTGGCCTAAGGTAC

When does DNA replication occur?

Occurs during "S" Phase of the Cell Cycle

How does DNA replicate?

DNA strands are separated and unwind

Original strands serve as template

Free floating nucleotides attach to complementary base pairs

Enzymes involved

What does semi-conservative mean?

Semi-conservative means that each daughter DNA consists half of parental DNA and half of new DNA.

What is the central dogma?

DNA -> RNA -> Protein

What is RNA made of?

Ribonucleic acid

Has ribose as sugar instead of deoxyribose

Always 1 stranded

Uracil (U) instead of Thymine (T)

C=G

A=U

What are the three types of RNA?

Messenger (mRNA)

Transfer (tRNA)

Ribosomal (rRNA)