Keystone Definitions - Part B

Any relevant info straight from part B of the keystone review packet

Cell Cycle

A repeated pattern of growth, DNA duplication, and cell division that occurs in eukaryotic cells.

What are the stages of the cell cycle?

Interphase, nuclear division*(meiosis or mitosis)*, cytokinesis

What purpose does Mitosis have?

Growth & Repair

What are the sections of interphase and what happens in each?

**G1 (Gap 1) Phase:** Cell grows

**S (Synthesis) Phase:** DNA is duplicated

**G2 (Gap 2) Phase:** More cell growth

What happens in Mitosis? (very broad, overall)

The nucleus divides

What are the sections of Mitosis?

Prophase, Metaphase, Anaphase, Telophase

What happens in prophase?

Chromosomes condense and are visible as **sister chromatids** (X’s).

Nuclear membrane disappears.

Spindle fibers form out of centrioles.

What happens in metaphase?

Spindle fibers connect to the centromeres.

Chromosomes line up in the **m**iddle of the cell.

What happens in anaphase?

Sister chromatids **separate**, pulling **a**way from each other and becoming individual chromosomes.

Chromatids move to opposite ends of the cell.

What happens in telophase?

Chromosomes decondense and start to look like chromatin again *(thread-like instead of rod-like)*.

Nuclear membrane re-forms around the chromosomes at each pole.

Spindle fibers break down.

Cytokinesis begins.

What happens during cytokinesis?

The cytoplasm along with everything else divides forming two daughter cells.

What are the sections of meiosis?

Meiosis I and Meiosis II each with it’s own set of PMAT + cytokinesis

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**Ex.** Meiosis II = Prophase II, Metaphase II, etc.

What happens in Meiosis I?

Separation of homologous chromosomes

What happens in Meiosis II?

Separation of sister chromatids (*identical copies of the same chromosome)*

Diploid

2 full sets of chromosomes

1 from each parent

Haploid

1 full set of chromosomes

What do both meiosis and mitosis result in? (Similarity)

Daughter cells that contain DNA

Mitosis: purpose, produces, outcome

**Purpose:** growth & repair

**Produces:** somatic cells *(body cells)*

**Outcome:** 2 genetically identical diploid daughter cells

Meiosis: purpose, produces, outcome

**Purpose:** reproduction

**Produces:** sex cells *(eggs & sperm; reproductive cells/gametes)*

**Outcome:** 4 genetically unique haploid daughter cells

What is the brief period in between Meiosis I and II sometimes known as?

Interkinesis

DNA

The macromolecule that contains genetic information

Genes

A segment of DNA that carries instructions to code for a protein.

Within a species, genes for the same trait *(i.e. eye color)* have the same location.

Alleles

A variation of a gene *(i.e. blue v.s brown eyes)* that can be expressed as a phenotype *(physical trait)*

How does allele domination generally work?

A dominant allele will always be expressed if present.

A recessive allele will only be expressed if a dominant allele is not present.

Chromosomes

A tightly coiled strand of DNA that contains thousands of genes linked together.

Traits

Inherited by the transfer of genetic material*(DNA)* from parent to offspring.

Each parents contributes one allele for each trait

How are dominant alleles written?

With capital letters

How are recessive alleles written?

With lowercase letters

Genotype

The actual alleles an individual inherits from their parents

Phenotype

The physical trait that is expressed

Punnett Square

A diagram that shows the probability of inheriting traits from parents

What is a genotype of Aa called?

Heterozygous

What is a genotype of AA or aa called?

Homozygous

Co-dominance

Both versions of the traits are fully and separately expressed.

**ex.** Black and White = speckled

Incomplete Dominance

Some alleles are neither dominant nor recessive, the heterozygous phenotype lies somewhere between the two homozygous phenotypes.

**ex.** Red and White = Pink

Sex-linked

Genes that are located on sex chromosomes.

X-linked traits are located on the X chromosomes and Y-linked are on the Y chromosome.

**ex.** color blindness

Polygenic

A trait produced by two or more genes.

Usually shows a range in phenotype.

**ex.** Skin color, eye color, height, personality

Multiple Alleles

Having more than two alleles for one gene

**ex.** blood type, fur color in rabbits

Allele(s) for O type blood

ii

Allele(s) for A type blood

I^A I^A or I^A i

Allele(s) for B type blood

I^B I^B or I^B i

Allele(s) for AB type blood

I^A I^B

Crossing Over

Segments of homologous chromosomes are exchanged during prophase I *(meiosis)*

A change in gene location will occur on both chromosomes resulting in cells that will be genetically different.

Nondisjunction

Chromosomes do not separate properly during cell division. This results in an extra or missing chromosome.

Duplication

Results in multiple copies of the same gene.

Translocation

Non-homologous chromosomes swap pieces of DNA.

Inversion

A segment of the chromosome breaks off and reattaches in the reverse direction.

Deletion

Deleted a segment of DNA

Insertion

Inserts a segment of DNA

What is a similarity between the way all living organisms(prokaryotes and eukaryotes) assemble proteins?

They do it through transcription and translation

Transcription = ________ → ________

DNA → mRNA

Translation = ________ → ________

mRNA → polypeptide

Transcription

DNA is transcribed into mRNA *(messenger RNA)*

Takes place in the nucleus*(eukaryotes)* or cytoplasm*(prokaryotes)*

Translation

mRNA is translated by the ribosome to produce an amino acid chain*(polypeptide/protein)*

Takes place in the ribosome which is found in the cytoplasm or the ER*(eukaryotes)*

Substitution/Point Mutation

Substitutes ONE nucleotide for another

What are the three outcomes of a mutation?

Silent, Missense, Nonsense

Silent Mutation

The nucleotide change does not result in the production of a different amino acid = protein function doesn’t change

**Ex.** AAA and AAG = Lysine

Missense Mutation

The change of nucleotide results in the production of a different amino acid.

Affects the phenotype

**Ex.** Sickle Cell Anemia = from GAG *(glutamic acid)* → GUG *(valine)*

Nonsense Mutation

The change of nucleotide results in a stop codon.

Incomplete protein = won’t function properly

**Ex**. UAC *(tyrosine)* → UAA

Frameshift Mutation

The insertion or deletion of a nucleotide(s). Unless it’s inserted or deleted in multiples of 3, all the amino acids after will be shifted.

Deletion

Deletion of a nucleotide

**Ex.** ATTACC → ATACC

Insertion

Insertion of a nucleotide

**Ex.** ATTACC → ACTTACC

Impacts of Genetic Engineering: Agriculture

1. Selective breeding
2. Cloning
3. GMOs

GE - Selective Breeding

Intentionally breeding specific organisms with a desired trait in order to produce offspring with the same trait. This has been done for years, even before the discovery of DNA

* Inbreeding

Inbreeding

Crossing individuals that are closely related

* Can cause health issues ***ex.*** *joint issues in closely breeding labrador retrievers*

GE - Cloning

Produces offspring that are genetically identical to the parents

GE - GMOs

The DNA sequence of organisms is intentionally changed so that they produce desired traits.

***ex.*** *insect/rot resistant plants, cows that produce more milk, pigs that produce more lean meat*

Impacts of Genetic Engineering: Medicine

1. Transgenic organisms
2. Prevention & treatment
3. Personal genome sequencing
4. Bacterial transformation
5. Gene therapy

GE - Transgenic Organisms

Genes from one organism are placed into another. *(****ex.*** *inserting DNA from a bacterium into a corn plant)*

These organisms are often used as model test subjects in medical research, simulating human disorders such as Alzheimer’s disease and arthritis.

GE - Prevention & Treatment

Preventing and treating disease. ***Ex.*** *making our food more nutritious. Creating strains of mosquitos that are incapable of transmitting particular pathogens.*

GE - Personal Genome Sequencing

Using DNA sequencing technology to have YOUR person genome sequenced.

*This provides information about your physiological and susceptibility to certain diseases.*

*It can also diagnose hundreds of diseases.*

GE - Bacterial Transformation

A piece of circular DNA(plasmid) is removed from bacteria and another gene is inserted.

This genetically modified plasmid is introduced into a new bacteria cell which then produced the protein coded for on the inserted gene.

***Ex.*** *This process is used to make Insulin for diabetes*

Impacts of Genetic Engineering: Forensics

1. Criminal justice
2. Conservation
3. Identification
4. Establishing paternity & Tracing ancestors

GE - Criminal Justice

The scientific study of crime scene evidence.

DNA fingerprinting has been used to *solve crimes, convict criminals, and even overturn wrongful convictions.*

GE - Conservation

Officials can use DNA fingerprinting to identify the African elephant herds where the animals were poached for their tusks.

*Help stop illegal trade*

GE - Indentification

DNA can be used to identify remains

GE - Establishing Paternity & Tracing Ancestors

Determining relationships using DNA tracing

Natural Selection

Organisms more fit for their environment will live longer and produce more offspring.

What does natural selection do over time?

Over time, beneficial traits *(adaptations)* will become more common in the population and increase allele frequency.

Why do larger populations have greater genetic variation than smaller populations?

The gene pool is larger

Why is variety and diversity in a population important?

So the population can meet various challenged in a changing environment.

Allows for natural selection to occur

Gives the species a better chance for survival

Factors that contribute to the development of new species

1. Genetic drift
2. Founder effect
3. Population bottleneck
4. Migration *(gene flow)*
5. Reproductive isolation

Genetic Drift

Random change in the frequency of alleles in a population over time

Founder Effect

Loss of genetic diversity when a new population is founded by a smaller group of organisms

Population Bottleneck

When an environmental event results in only a few individuals surviving, and the loss of a lot of genetic variation.

Migration (gene flow)

Movement of genes into/out of a population

Reproductive Isolation: Definition + how it occurs

Prevents a population from interbreeding

Can lead to **speciation**


1. Behavior Isolation
2. Geographic Isolation
3. Temporal Isolation

Speciation

Forming of a new species

Behavioral Isolation

Difference in courtship rituals

Geographic Isolation

Physical separation by a geographic barrier *(mountain, body of water, etc.)*

Temporal Isolation

Reproduction occurs at different times

Mutations: What they lead to, effects on genotypes and phenotypes

Lead to individuals with genetic differences

Increases genotypic variations and therefore, phenotypic variation as well.

Where do variations in structure/form between come from in organisms?

Changes in the genetic code *(mutations)*

What kind of proof provides the best evidence that two species descended from a common ancestor?

Shared physical characteristics *(anatomical structure)*

Morphology (anatomical and physiological): Definition and Examples

Study of the form of living things


1. Homologous structures
2. Vestigial structures
3. Analogous structures

Homologous structures

Similar structures that suggest evidence of common ancestry

* Similar structure, different function due to being used in different environments
* Result of divergent evolution (common ancestor)

Vestigial Structures

Structures with little to no function to an organism

* Could be leftover from an ancestor that has used the structure, and thus could provide evidence of divergent evolution

Analogous Structures

Similar structures that evolved independently in different organisms due to serving similar purposes

* Different structure, similar function *(ex. wings)*
* Result of convergent evolution, therefore not related

Paleontology (Fossils): Definition and Examples

Study of prehistoric life through the fossil record

* The fossil record reveals a history of the **types** of organisms that have lived on Earth (including now-extinct species) and the **ages** of those fossils


1. Transitional Fossils

Transitional Fossils

Link ancestral species to their descendants and are critical for piecing together evolutionary history