8th Grade Science-Genetics and Heredity



Life Science- 5.3.8.D.2, 5.3.8.D.3

GENETICS & CLASSIFICATION

Heredity  

Gregor Mendel

 Austrian Monk



studied garden pea plants to unveil patterns of heredity



Developed the Laws of Inheritance



Mendel noticed that traits from the pea plant parents didn’t always show up in their offspring

Heredity 

2 types of traits were identified:



Dominant trait – trait that appears in the offspring, offspring only needs one dominant allele from the parent to show up



Recessive trait – trait that fades in the background or may not show up in the offspring, only shows up if the offspring gets two recessive alleles from their parents



Mendel noticed that certain traits would reappear in later generations

Genes Mendel discovered that each individual carries 2 sets of characteristics (genes)

Each offspring has two forms of a gene (one from each parent) Genes - carry information that Genes determines your traits.

Genes Where are They? 

Genes hang out all lined up on thread-like things called Chromosomes Chromosomes..  The chromosomes and genes are made of DNA which DNA  which is short for deoxyribonucleic acids  Chromosomes are found inside cells 

Specifically in the nucleus nucleus of  of the cell. cell. (the nucleus is sort of like the brain of the cell)

Genes 

 How Do Genes Work? 

Genes carry instructions for making proteins in the cell.  Proteins Proteins are  are the building blocks for everything in your body. body. Did you know? Each cell in the human body contains 25,000 to 35,000 genes.

9/25/14 

Do Now: Where are Genes found and what are they made out of ?



SWBAT- Understand how traits and characteristics are inherited from generation of organisms to the next

Genes are made of DNA DNA and  and hang out all lined up on thread-like things called Chromosomes Chromosomes..

http://youtu.be/Mehz7tCxjSE?t=13s

 Alleles  Allele - different form(s) of a gene, responsible responsible for hereditary variation.



Dominant trait – appears if it inherits the gene for that Dominant trait trait from either parent; will always be expressed and will mask  a recessive trait. Shown by capital letter(s). “



”

Recessive trait – appears only if it inherits that trait Recessive trait from both both parents  parents and can only be expressed if there are no dominant alleles present; shown by lower case letters.

 Alleles 

Genotype –The alleles present in an organism. inherits from its parents, the actual gene makeup represented by letters. BB Bb bb



(Example: BB, (Example: BB, Bb, or bb) bb) Purebred , also called Homozygous Homozygous consists  consists of gene pairs with genes that are the same same.. (Example: RR -or- rr  )

“

”

“

”

“    

”

Hybrid , also called Heterozygous Heterozygous and  and consists of gene pairs that are different different.. (Example: Rr  )  Note: The capital letter always is written first.

“

”

“

”

This is the "internally coded, inheritable information" carried by all living organisms. is .

 Alleles 

Phenotype – is the physical appearance of a trait. 

What it looks like… Example: blue eyes or brown hair

Phenotype--------- Red 

Red

These are the physical parts, anything that is part of the

White

9/30/14 

Do Now: What are the two kinds of genotypes alleles ?



SWBAT- Understand how traits and characteristics are inherited from generation of organisms to the next

Punnett Square Punnett Square - a diagram used to predict outcomes of genetic combinations. The Punnett square is a summary of every possible combination combination of  of one maternal allele with one paternal allele for each gene being studied in the cross. S t ep e p s f o r U s i n g t h e P u n n e t t s q u a r e: e:  

1) One parent s alleles (genotype) go along the top 2) The other parent s alleles go down the side. side. 3) You fill in the squares like doing the communicative ’

’

property of multiplication multiplication..

Punnett Square Practice: The Parents eyes are Brown and Blue B= brown eye color

b= blue eye color

Fill out the Punnett square on the right to help answer the following questions.

F

BB

B b

M

This organism has __50______% or  ___1/2_____chance of receiving brown eyes. brown eyes.

 b

Bb

bb

This organism has __50______% or  _______1/2_____ chance chance of receiving blue eyes.

 b

Bb

bb

The possible g e n o t y p e s    are:  are: Bb and bb

The Cell and Inheritance Key Concepts •What role do chromosomes play in inheritance? •What events occur during meiosis? •What is the relationship between chromosomes and genes?

Key Terms Terms Meiosis

Chromosomes and Inheritance 

1903- Walter Sutton was studying chromosomes in grasshoppers.



Found that the body cells of grasshoppers have 24 chromosomes, but the sex cells only had 12 ( exactly half)

Chromosome pairs 



Sutton observed that when a sperm cell and an egg cell joined in fertilization fertilizatio n the resulting fertilized egg again had 24 chromosomes chromosomes.. Chromosomes exist in pairs. One chromosome in each pair came from the male parent and one came from the female parent

Genes on Chromosomes 

Sutton knew that alleles exist in pairs in an organism and one alleles comes from the female parent and the other from the male parent



Sutton realized that the paired alleles are carried on paired chromosomes



Chromosome theory of inheritance – genes are carried from parents to offspring on chromosomes



Meiosis

http://youtu.be/qCLmR9-YY7o?t=6s

10/3/14 

Do Now: Chromosomes exist in pairs, who do they come from?

One chromosome in each pair came from the male parent and one came from the female parent 

SWBAT- Understand how traits and characteristics are inherited from generation of organisms to the next

Meiosis 

Meiosis – the process by which the number of chromosomes chromosom es is reduced by half to form sex cells – sperm and egg



The chromosome pairs separate and are distributed to two different cells



Each of these 2 cells has half the number of chromosomes, but these chromosomes still have 2 chromatids



In the second part of Meiosis, these chromatids separate and the cells divide resulting in 4 sex cells, each with half the number of chromosomes of the original cell

Meiosis

Meiosis and Punnett squares 

Punnett squares show what occurs during meiosis



When chromosome pairs separate and go into different sex cells, so do the alleles, too

10/7/14 

Do Now: What are chromosomes composed of and what are Genes?

DNA and sections of a DNA molecule

Objective: SWBAT comprehend/distinguish what forms the genetic code, how a cell produce proteins and how mutations affect an organism

 A Lineup of Genes 

Human body cells have 23 pairs of chromosomes or 46. Each chromosome has many genes. (around 25,000 total)



Each gene controls a trait



One chromosome pair is from the female parent and one is from the male parent



This organism is heterozygous for some traits and homozygous for others Each have the same gene “A and a”, b and B”

Which is Which?



What do genes control?



Objective: SWBAT comprehend/distinguish what forms the genetic code, how a cell produce proteins

The DNA Connection Key Concepts: What forms the genetic code? How does does a cell produce produce proteins? How can mutations affect an organism?

Key Terms: Messenger RNA Transfer Tran sfer RNA R NA

The Genetic Code 

Main function functio n of genes is to control the production of proteins

Genes and DNA: Chromosomes are made of DNA. Genes are sections of a DNA molecule that codes for one specific protein. May contain contain several hundred hu ndred to a million or more base pairs (EX:  AGGT  AG GTCA CAC CGAA GAATTTT TTTTC CC GG)



What is a Protein?

A protein is simply a long chain of amino acids linked together by bonds. bonds . The backbone of amino acids form strong covalent c ovalent bonds and the actual amino acids form temporary weak bonds. The most important quality to understand about proteins is that the position of their amino acids determine their function.

Word Introductions 

t hat, when joined together, make Nucleotides: molecules that, Nucleotides: up the structural units of RNA and DNA.



Amino



RNA: a nucleic molecule similar to DNA that delivers DNA's RNA: genetic message to the cytoplasm of a cell where proteins are made

acids:: A group of 20 different kinds of small acids molecules that link together in long chains to form proteins; building blocks of protein.



DNA: a nucleic acid that contains the genetic instructions DNA: used in the development and functioning of all known living organisms and some viruses

Types of RNA 

Messenger RNA – copies code from DNA in the nucleus and carries message to ribosomes in the cytoplasm



Transfer RNA – carries amino acids to ribosome and adds them to the growing growing protein molecule molec ule

Order of Bases ma de up of 4 different nitrogen bases • DNA molecule is made  Adenine (A), Thymine Thymine (H), Guanine (G) and Cyto Cytosine sine (C) ni trogen bases along a gene forms a genetic • The order of the nitrogen code that specifies what type of protein will be produced. amin o acids – A group of 3 base pairs • Proteins are made of amino codes for a specific amino acid

• Ex. CG CGT T = alanine alan ine (an amino acid) t he 3 base bas e code code units determines the order of the • The order of the amino acids and makes ma kes the different proteins

10/10/14 

Do Now: Name the 4 nitrogen bases found in DNA

 Adenine (A), Thymin Thyminee (H), (H), Guanine (G) and Cytosin Cytosinee (C) (C)

Objective: SWBAT comprehend/distinguish what forms the genetic code, how a cell produce proteins

How Cells Make Proteins (Protein Synthesis) The Role of RNA (Ribonucleic (Ribonucleic acid) t akes place on ribosome in i n cytoplas cytoplasm m • Protein synthesis takes (which is outside the nucleus) messe nger to take the DNA  s information • RNA acts as a messenger in the chromosomes (in the nucleus) to the ribosomes in the cytoplasm ’

simila r to DNA, yet different in some key ways: • RNA similar  –  –  –  –

single strand ribose sugar   Bases – same - adenine, guanine and cytosine   different – uracil instead of thymine

The steps of protein synthesis are

1.

Transcription

2. Translation

10/15/14 



Do Now: List the 2differences between DNA and RNA  – single strand  – Bases – same - adenine, guanine and cytosine  –   different – uracil instead of thymine Objective: SWBAT comprehend/distinguish what forms the genetic code, how a cell produce proteins

Translating the th e Code Transcription-First Step: 1. DNA molecule unzips between base pairs 2. DNA directs the production of a strand of messenger RNA 3. To form the RNA strand – RNA bases pair with DNA bases. Guanine with Cytosine, but uracil pairs with adenine instead of Thymine

Translating the th e Code Transcripti ranscription-Second on-Second step: 1. Messenger Messe nger RNA leaves nucleus and attaches atta ches to a ribosome in the cytoplasm 2. Messenger Messe nger RNA provides the code to make the protein molecule 3. The ribosome moves along the th e messenger RNA strand

10/16/14 

What carries instructions for making protein in the cell?

Genes carry Genes carry instructions for making proteins in the cell. 

Objective: SWBAT comprehend/explain what forms the genetic code, how a cell produce proteins and how mutations affect an organism

Translating the Code Translation-First Step 1. Molecules Molecule s of transfer RNA attach to messenger RNA 2. Bases of transfer RNA read the message by pairing up 3letter codes codes to bases of messenger RNA 3. Molecules of transfer RNA carry specific amino acids that link in a chain 4. Order of amino acids is determined by order of 3-letter 3-l etter code on messenger RNA

Translating the th e Code Translation-Second step 1. Protein molecule m olecule grows longer as each transfer RNA adds an amino acid 2. When done the transfer RNA is released into the cytoplasm and can pick up another amino acid 3. Each Ea ch transfer amino acid picks up the same type of amino acid

Translating the Code Summarized 1- Messenger RNA Production 2- Messenger RNA attaches to a Ribosome 3- Transfer RNA attaches to Messenger RNA 4-Protein Production continues 1&2- Transcription 3&4- Translation

10/21/14 

What part of the Cell does Transcription take place and where does Translation take place?



Transcription- In the Nucleus



Translation – In the cytoplasm



Objective: SWBAT comprehend/ explain how mutations affect an organism

Mutations 







 A mutation is any change in a gene or chromosome Mutations can cause c ause a cell to produce an incorrect protein during protein synthesis.  As a result of a mutation, the organism s trait or phenotype, may be different from  what it normally normally would hav havee been ’

If a mutation mut ation is i s in a body cell, it will not n ot be passed on o n to the offspring. If it is a sex cell, it can be passed on o n and can affect the offspring s phenotype ’

Substitution

Insertion

Deletion

Types of Mutations Some mutations happen during DNA Replication:  

 A single base may may be be substituted for another One or more bases may be removed from a section of DNA or new bases base s inserted

Some mutations happen during Meiosis: 

Chromosomes don t separate correctly



Cell can end up with too many or too few chromosomes

’



Cell could end up with fragments of chromosomes

Effects Ef fects of Mutations 

Mutations introduce int roduce change change in an organism and so s o are a source source of genetic geneti c  variety



Some mutations mutatio ns are harmful, some are helpful, and some s ome don t affect the organism ’



Whether a mutation is harmful or not depends partly part ly on the environment environment 

A mutation causing an albino animal in the  wild would would be harmful, but if the animal lived in the zoo, it would not matter

Effects Ef fects of Mutations 

Helpful mutations improve an organism s chances for survival and reproduction ’





Ex. Bacteria that have mutations that have given them resistance to antibiotics antibioti cs are more likely to survive and reproduce

Harmful effects of Mutations are diseases or illnesses such as Sickle cell anemia (the blood cell is misshaped) this is an example of Substitution mutation 

Heart disea disease, se, cancer, cancer, and Alzheimer's are due to mutations in several genes.

Sources 

http://www.grasshoppercontrol.com/



http://www.todayinsci.com/11/11_10.htm



http://www.accessexcellence.org/RC/VL/GG/images/genes. gif