Science Unit Review

All organisms have traits that make them unique and distinguishable from one another.

Variation is a difference in traits between organisms.

Can affect whether or not an organism can survive in a particular environment

Traits help organisms survive and function

Bell curve

Shows that most of the data falls in an area around the top

This area at the top is what is considered “normal”

Review Questions!

In science, the difference in the physical features of an organism is called…

A. a trait

B. normal

C. a bell curve

D. variation

When graphing traits in a population of organisms, the versions of a trait near and at the top of a bell curve are considered to be

A. the least popular versions

B. normal

C. unique

D. mutations

Mutations

changes made to the message are what also happens sometimes to DNA when they’re being copied (TLDR: mutations are changes made to the DNA)

DNA: Deoxyribonucleic Acid

All of the instructions of how to build the specific organism

Found in the nucleus of the cells (NEVER LEAVES THE NUCLEUS!!)

Double helix structure

Structure of DNA

Sugar & phosphates on the side

Nitrogen bases in the middle

Sugar + phosphate + base = nucleotide

What makes organisms/species different?

The order of the bases

How much DNA they have

The Bases

(A) Adenine, which pairs with Thymine

(T) Thymine, which pairs with Adenine

(G) Guanine, which pairs with Cytosine

Apples in Trees

Cars in Garage

Genes are part of the DNA (which is from your parents) that have information that control a trait

Genes are found in DNA and they condense to make chromosomes

A typical child has 46 chromosomes, 23 from each parent

Mutations

Substitution: one or more bases are traded

Insertion: one or more bases are added

Deletion: one or more bases are removed

Organisms inherit traits from their parents, this inheritance occurs because of genes

Chromosomes

Contain a set of instructions given to an organism by its parents

Are located in the nucleus of an organism’s cells

Are made up of DNA

DNA is tightly packed inside each chromosome

Genes

Genes are sections of chromosomes

Genes contain codes for the organism to built proteins

Different genes make different proteins

The size & shape of each protein is determined by the code in each gene

Each protein has a different function in the body

Proteins determine traits - how an organism looks & functions

Flowchart

Chromosomes are made up of Genes

Genes code for proteins

Proteins give us our traits

Alleles are different forms of a gene

They are always represented by a letter

A capital letter means..

DOMINANT allele

This allele has more of a say in what the trait looks like

A lowercase letter means..

RECESSIVE allele

This allele doesn’t have much of a say unless the dominant allele isn’t there

Children of the same parents might look a little different because it depends on which alleles each parent gives them.

Homozygous: Letters are the same

ex: HH or hh

Heterozygous: Letters are different

ex: Hh

Genotype: The combination of alleles and organism has

Phenotype: An organism’s physical appearance

The Genotype controls the phenotype or genes determine how you look

Hair example

HH = Both brown hair alleles, pass on brown hair

Hh = Brown hair allele and red hair allele (which is hidden), pass on brown hair

hh = Both red hair alleles, pass on red hair

Animals that blend in with their surroundings have a higher survival rate compared to those who don’t blend in

Ex: In a light colored sandy environment, light brown mice are more likely to survive their predators compared to dark brown mice

But if there was a sudden volcanic eruption and the environment changed to one covered in dark lava rock, the dark brown mice are more likely to survive compared to the light brown mice

When animals have a beneficial trait, they are able to survive & increase in number (reproduce)

Predators that are extremely good at hunting can end up eating all of the prey

This is bad because then they have no more food and then they have to look somewhere else for food or else they will die off.

Diversity

Species that have great diversity have a higher survival rate

This is because they have different traits that distinguish them from one another. So, if something happens to wipe out one version, there are still other versions that live.

So, diversity in organisms increases their ability to survive during changing environmental conditions

Recombination

Recombination (or crossover) is when chromosomes become twisted together and some of their genes change places

The longer the chromosome, the more it can cross over.

Most chromosomes cross over in at least 1-2 places

Crossovers & recombination creates greater diversity

Chromosome recombination increases the survival of a species

Fertilization

To make an offspring, a sperm cell and an egg cell fuse to form a zygote

The female and male chromosomes make a pair, creating a new combination of alleles different from both parents

Vocabulary Definitions

Base pairs are the code for traits in DNA

DNA coils to be packaged into chromosomes

DNA that gets damaged when being copied can cause mutations

Mutations can create a different genotype

Genotype tells the cells how to fold the proteins

Proteins fold to show the phenotype

DNA has information that codes for a trait which leads to genes

Genes are different forms of alleles

Alleles combine to make the trait’s genotype

Punnett squares are used for determining the probability of getting a certain genotype

Punnett squares are used to tell the probability of a certain phenotype (trait)

Genetics Article

Humans can selectively enhance desired traits in other living things 2 different ways

Seletive breeding

Carefully choosing parents for breeding that show the desired characteristics

Genetic engineering

Technology is used to transplant genes for a desired characteristic into an organism

Genes are made of DNA

Genes are inside chromosomes of cells

The instruction for a certain trait are inside genes

Genes are the recipe, proteins are the “cookies” or whatever you’re trying to make

DNA never leaves the nucleus of a cell

The nucleus sends out RNA w/ the “recipe” to ribosomes

Ribosomes make proteins

Mutations can be…

Harmful

Benficial

No effect at all

Fitness

An organism’s ability to survive and reproduce in its environment.

Adaptation

A trait that an organism has which helps them to survive and reproduce in their environment.

Mutation

A change in an organism’s genetic code that results from an error in reproduction.

Genetic Engineering

The manipulation of an organism’s genes using biotechnology techniques

Artificial Selection

Also known as selective breeding

Artificial selection needs trait variation

Humans select favorable traits

Benefits: Reliable food sources, profit for farmers, hardy plants that grow well

Concerns: “Undesirable” traits will disappear, decreases genetic variation, inbreeding can produce offsprings that aren’t able to reproduce, can reduce food and shelter for birds and insects

Natural Selection

A process where organisms that have the highest fitness survive and pass on their traits through reproduction.

Traits decided by the environment, weaker traits disappearing over time & organisms adapting.

Natural selection needs trait variation

The environment selects favorable traits

When organisms that are better adapted to live in their environment, survive and are able to make more babies

Domestication

Cultivating wild plants for the use of humans. It is artificial selection.

Inbreeding

Inbreeding is keeping desired characteristics by crossing organisms with similar traits, this is artificial selection.

Breed(s)

Organisms with different traits. It could be either artificial or natural.

Hybridization

Hybridization is getting a blend of traits by crossing organisms with different characteristics. This is artificial selection.

How are genes, proteins, and traits related?

Genes are different forms of alleles, alleles make up genotypes, genotypes tell the cells how to fold proteins, and proteins fold to show the phenotype. (Phenotype is an organism’s physical appearance OR just traits) TLDR: Genes are the recipe for proteins, proteins show the traits.

What happens when the original “recipe” changes? What is the science word for this change?

If the original “recipe” changes the cookies change. The science word for this is: mutation

How are selective breeding and genetic engineering different?

Genetic engineering uses technology to transplant genes for a desired characteristic into an organism. Meanwhile, selective breeding is carefully choosing parents for breeding that show the desired characteristics.

Adaptations

How did it happen?

Organisms change how they use traits to help them survive better.

New trait?

No new trait(s)

Speed of change?

Slow

How many generations?

Multiple generations to see change

Affect on population?

Any individuals who adapt live

Mutations

How does it happen?

A mistake in the DNA changes them

New trait?

New trait(s)

Speed of change?

Fast (born w/ it)

How many generations?

One individual changes

Affect on population?

Change may only help 1 individual (can spread through breeding though)