Biology Final Study Guide

What are Mendelian traits

dominant and recessive traits

Dominant alleles

The allele that is always shown

Ex. Rr R= the dominant trait

Recessive traits

Masked by dominant allele and is only shown when dominant allele is not present

ex.) Rr r= recessive rr= the recessive is shown

Modes of Inheritance

co-dominance, incomplete dominance, multiple alleles, polygenic traits, sex-linked

co-dominance

both alleles contribute to the phenotype

Ex. BB x WW = BW → white chicken with black spots

→ spotted

Incomplete Dominance

One allele is not completely dominant over the other

* they blend together

RR x WW = RW → red x white= pink

Multiple alleles

More than 2 alleles can exist for a trait

* Ex. Blood A,B,O
* Eye color in fruit flies
* Rabbit coat color

Polygenic traits

Traits controlled by 2+ genes

* phenotypes exist in a gradient

Ex. Human eye color, hair color, and height

Sex-linked

Genes located on either x or y

* x linked are more common because boys don’t have another x chromosome to dominate their diseased x
* Sex linked disorders: colorblindness, hemophilia, duchenne Muscular Dystrophy

Punnett squares

shows the principle of segregation

* alleles are separated from their partner during meiosis

Major events in meiosis

* Major Event 1 = Tetrads form

→ happens in prophase 1 where the homologous chromosomes pair up to form tetrads for crossing over

* Major Event 2 = Crossing Over

→happens in prophase 1 when the homologous chromosomes exchange sections

→ This increases genetic diversity

* Meiosis 1 =

→ Metaphase 1 : tetrads line up on metaphase plate → Anaphase 1 : tetrads separate and chromosomes move to opposite poles

→ Results in 2 non-identical haploid cells

* Meiosis 2 =

→ No DNA replication occurs before hand

→ process exact copy of mitosis

Results in 4 non-identical haploid cells

results of meiosis

Meiosis 1 = 2 non-identical haploid cells

Meiosis 2 = one diploid cell forms **4 non-identical haploid gametes**

Inheritance types observed in blood type

A , B , AB , and o

* inherited through co-dominance
* Blood is determined off 2 types of antigens : type A and type B
* type A = antigen A ; type B = antigen B ; type AB = both antigens ; type o= neither antigens

Homologous chromosomes

Pair of chromosomes with one paternal and one maternal

* same length, shape, and set of genes

Homologous chromosomes involvement in crossing over

The homologous chromosomes, one set of maternal and one set of paternal, line up in the middle of the metaphase plate to form tetrads. They then exchange sections and increase genetic diversity.

Karyotypes

a display of an individual’s complete set of chromosomes

* determine the gender by the last two set of chromosomes: if there are 2 X chromosomes, it is a girl. If there is 1 Y and 1 X chromosome, it is a boy.

What gender is this:

Male

Nondisjunction

Chromosomes fail to separate properly during meiosis

* Leads to aneuploidy

aneuploidy

condition of having an abnormal amount of chromosomes in a haploid set

* monosomy
* Trisomy

What is genetic engineering

Human manipulation of an organism’s DNA

* made possible by the ability to find particular sections of DNA
* Results in GMOs

What is a GMO

Genetically modified organism

What is selective breeding

* humans breed organisms with desired characteristics to produce the next generation
* “select” specific traits to pass on

Types of selective breeding

Hybridization and Inbreeding

* DNA is not being messed with by humans

Hybridization

crossing of dissimilar individuals to bring best of both worlds together

* Ex.) Brangus cattle

Inbreeding

Continued breeding of individuals with similar characteristics

* ensures you know what the offspring looks like
* Can create serious problems as you bring together 2 recessive alleles

How do you increase variation

By introducing mutations

* using radiation or chemicals

Why do scientists do this?

To study genes and to introduce new beneficial traits

* Critical in agriculture

Types of Genetic Engineering

1. PCR
2. Recombinant DNA technology

What does PCR stand for

Polymerase Chain Reaction

What does it do

Makes billions of copies of a target segment of DNA in a few hours

* Quick and doesn’t need large amounts of DNA

Why is this important?

* Allos for a particular section of DNA to be identified and studied

What is Recombinant DNA technology

Joining together DNA from 2 or more sources

* can change the genetic makeup

Why is it important

Introduces new genes into another organism’s existing DNA

* DNA is cut, altered, and then put back together

What are uses of recombinant DNA in bacteria

bacteria is used to produce many important substances for the pharmacies

* Produces insulin, growth hormone, and clotting factor in large quantities

What are transgenic organisms

Organisms that possess a useful gene from other organisms

* made by way of recombinant DNA

→ Meaning, the properties in the bacteria that are easily manipulated for beneficial traits are transferred into animals

Types of transgenic organisms

Transgenic bacteria, plants, and animals

Transgenic Plants- what are they important to? Why?

food supply

GMO crops help farmers to be more productive while reducing overall costs

* pest resistant
* heat resistant
* higher nutritional content

Transgenic Animals

Genes for better meat, resistant to disease, faster growing animals

What is a spider goat

Goat given a gene to produce spider silk

* produces milk with silk protein
* can be spun into spider silk = bio steel

What is biosteel

7-10x stronger than steel

Resistant to extreme temperatures

→ Can make bulletproof vests

Cloning

Creating a genetically identical organism

Example:

Scottish scientists were the first to clone a mammal in 1996

* Created a sheep named Dolly who suffered from lung cancer and arthritis
* Put down by lethal injection in 2003

Cloning steps

1. obtain an egg cell

* Remove the nucleus


2. Obtain a somatic (body) cell from the “mother”

* Dolly’s cell came from an udder


3. Place the somatic cell into an empty egg

* Grow the embryo
* Implant into a surrogate mother


4. Genetic identity equal to the somatic cell donor

Cloning issues

Less than 2% embryos result in live birth

* Dolly was a 1/276
* Of those, many had serious health problems

Benefits of cloning

1. if improved, could reproduce animals with specific benefits

* Mass produce these animals


2. Repopulation of endangered species
3. Produce whole human organs from a couple of cells
4. Stem cell research using cloned embryos

Gel electrophoresis

A strand of DNA is partially replicated using PCR

* electrophoresis separates DNA pieces by size to create a unique gel of bands unique to individuals
* used in DNA fingerprinting

What are the two types of rate of evolution

Gradualism and punctuated equilibrium

Gradualism

* Slow, steady change over time
* slowly see change in fossils

Punctuated Equilibrium

Stable periods interrupted by rapid change of species

* when changes happen quickly

Who is Charles Darwin

An english naturalist in the 1800’s who changed the way we viewed the world

What theory did he develop and what did it do

The theory of natural selection

* Gave scientific principles to what people observed (that things change over time)

Who was Lamarck

A scientist who created the original theory of evolution before Darwin, but was incorrect in many ways

What did he believe?

Individual organisms could change __in their lifetime__ by selectively using or not using organs

* These __acquired traits__ were then passed on to the offspring

Who was Malthus

Another scientist before Darwin who came up with the idea that overpopulation lead to disease, famine, and war

How did Darwin apply Malthus’ theory?

The overwhelming majority of offspring die, so only the fittest survive

What did Hutton and Lyell come up with

They observed since the earth is extremely old. Processes that change Earth are the same ones today.

How did Darwin apply this

If Earth changes over time, why can’t life change too

Fitness

How likely you are to survive and reproduce

Adaptations

Things that increase ability to survive/reproduce

Where was natural selection proposed

in Darwin’s book - On the Origin of Species

What is it?

Says that organisms with variations most suited to their environment will survive and have offspring

What are natural selection’s 3 conditions

1. there is a struggle for existence
2. variation and adaptation are found within a species that is heritable
3. survival of the fittest occurs

Artificial selection

selecting the best traits that are heritable and producing them to the next generation

what are the 3 types of selection

directional

stabalizing

disruptive

Directional selection

an extreme phenotype is favored

* causes allele frequency to shift over time in that direction

Stabilizing selection

Eliminates the extremes of a phenotype

* the intermediate is favored

Disruptive selection

favors the extremes and eliminates the middle phenotype

* can lead to speciation

Genotype

The genetic makeup of an organism

Phenotype

Observable characteristics

Gene pool

The possibilities for the species

* species share a common group of genes

Gene/ allele frequency

Number of times an allele shows up in a gene pool

Reproductive isolation

When gene flow between 2 groups stops, so they can no longer reproduce

What are the 3 types of speciation / reproductive isolation

behavioral

geographical

temporal

Homologous structures

Structures with the same origin, but different function

* Animals that are related (have a common ancestor) but live in different environmens

Analogous structures

Different origin, same function

* They aren’t related but use their structures the same

Vestigial structures

Structures that no longer have a function but were onced used in the ancestor

Vestigial examples

* whale pelvic girdle
* Human appendix and tailbone
* Eyeballs in blind creatures

Divergence

Evolutionary process where a species separates resulting in related species becoming more and more dissimilar

Convergent Evolution

Unrelated organisms evolving similar traits due to similar niches

* Ex. penguins and dolphins

Co-evolution

When a species evolving affects the evolution of another species

Ex.) if an animals gains better camouflage, its predator might gain better eyesight

Adaptive radiation

A single species diverges into multiple different species

ex.) Darwin’s finches

Morphological change

appearance that benefits an organism’s survival

behavioral adaptations

a behavior that benefits an organism’s survival

Physiological adaptation

internal change that benefits an organism’s survival

Genetic Drift

When an allele becomes more or less common in a population due to chance

* Meaning, it is random

What are the two types

Bottleneck effect

The founder effect

Bottleneck effect

An external event (natural disaster) kills off many in the population → the new population has different allele frequencies than previously

* Ex.) Pingelap when a typhoon and starvation hit

The founder effect

A few individuals colonize a new habitat

* can cause major changes in allele frequencies
* Ex. the Amish founders with polydactyly and dwarfism

Human evolution

come back to

what were the 3 major mass extinctions

1. Snowball earth (caused by glaciation)(increase of oxygen levels)
2. Pangea forms (upsets ocean currents) (the Great Dying)
3. Meteor hits Earth (meteor that kills the dinos)

What did the snowball earth usher in

Cambrian explosion

The Great Dying

Pangea forms, volcano erupts, Earth temp rises, 96% of all life goes extinct

What does this usher in

The Mesozoic: Age of the reptiles

Meteor

wipes out dinos and 76% of life

What does this usher in

the Cenozoic: Age of mammals

What is a half-life

Time required for half of the radioactive atoms to decay

* how long something takes to decay by 50%

Characteristics of first life

* unicellular bacteria (prokaryotes)
* 3.6 BYA
* a billion years after Earth’s formation
* Fossil evidence through cyanobacteria’s stromatolites

Absolute dating

More precise than relative dating

* relies on radioactive isotopes which break down at a steady rate

Relative dating

Generic method of dating fossils using layers

* uses index fossils to give an approximate date for other things

Importance of fossils

1. Show evolution
2. Reveal different species
3. Can be used for dating