Genetics Ms Mahoney MCAS Biology

Central Concepts: Genes allow for the storage and transmission of genetic information. They are a set of instructions encoded in the nucleotide sequence of each organism. Genes code for the specific sequences of amino acids that comprise the proteins characteristic to that organism. 3.1Describe the basic structure (double helix, sugar/phosphate backbone, linked by complementary nucleotide pairs) of DNA, and describe its function in genetic inheritance

DNA Structure Two strands (double helix) Sugar and Phosphate backbone Nucleic Acid – Made of nucleotides – 4 different kinds Adenine : A Guanine: G Thymine: T Cytosine: C – A pairs with T – G pairs with C

DNA Function Holds genetic information – For you (now) and your kids (future) Code for proteins

Central Concepts: Genes allow for the storage and transmission of genetic information. They are a set of instructions encoded in the nucleotide sequence of each organism. Genes code for the specific sequences of amino acids that comprise the proteins characteristic to that organism. 3.2Describe the basic process of DNA replication and how it relates to the transmission and conservation of the genetic code. Explain the basic processes of transcription and translation, and how they result in the expression of genes. Distinguish among the end products of replication, transcription, and translation.

Replication DNA make copies of itself when new cells are being made – Happens before mitosis and meiosis – Very important that the copy is the SAME

Replication Steps 1.DNA unwinds (opens up) 2.DNA polymerase (enzyme) adds nucleotides to the new strand (complementary) 3.Two new strands are formed – Each strand has an old copy and a new copy

Protein Synthesis Making of Proteins Also called gene expression Two parts: transcription and translation Transcription – Make RNA from DNA for a certain protein Translation – Make protein from RNA

Transcription

Transcription Steps Happens in the nucleus 1.Polymerase (enzyme) attaches to DNA 2.RNA is made based on the DNA strand RNA: one strand, nucleic acid, AUCG

Translation

Translation Step Happens on the ribosomes on the ER or in the cytoplasm 1.RNA attaches to the ribosome 2.tRNA “reads” the RNA and brings the matching amino acid based on the codon

Codons 3 nucleotides on RNA – Code for 1 amino acid Remember amino acids combine to make proteins You can use a code box to determine the amino acid

Central Concepts: Genes allow for the storage and transmission of genetic information. They are a set of instructions encoded in the nucleotide sequence of each organism. Genes code for the specific sequences of amino acids that comprise the proteins characteristic to that organism. 3.3Explain how mutations in the DNA sequence of a gene may or may not result in phenotypic change in an organism. Explain how mutations in gametes may result in phenotypic changes in offspring.

How to talk about genes? Genotype – DNA involved in the genes – Two copies (one from each parent) Called alleles – Example: BB, Bb, or bb Phenotype – Physical appearance of the gene – Example: brown hair, blue eyes, purple flowers

Mutations Mutations: change in the DNA – Most mutations don’t do anything – Some mutations are harmful Examples: change proteins, cause cancer Mutations in body (somatic) cells – Affect the person Mutation in sex (gametes) cell – Affect the children (offspring)

Mutations Mutation during REPLICATION – DNA will have the mutation from now on RNA and protein made from this DNA will be mutated Mutation during TRANSCRIPTION – RNA will be affected this one time Mutation during TRANSLATION – Protein will be affected this one time

Central Concepts: Genes allow for the storage and transmission of genetic information. They are a set of instructions encoded in the nucleotide sequence of each organism. Genes code for the specific sequences of amino acids that comprise the proteins characteristic to that organism. 3.4Distinguish among observed inheritance patterns caused by several types of genetic traits (dominant, recessive, codominant, sex-linked, polygenic, incomplete dominance, multiple alleles).

Inheritance Inheritance: passing of genes to offspring – After meiosis, gametes from each parent fertilize and make a zygote Alleles: different variations of the same gene – Hair color: ________ or _________? – Flower colors: _______ _______ ______? – Homozygous: same alleles – Heterozygous: different alleles

Alleles Dominant alleles – Allele that when present is physically seen – Shown as a Capital Letter – Autosomal or sex linked Recessive alleles – Allele that when present (in one copy) is not physically seen – If you have two copies, then it is seen\ – Shown as a lowercase letter – Autosomal or sex linked

D vs r example Flower Color – Red is dominant (capital R) – White is recessive (lower r) – If you have the genotype RR the flower color is ______________? – If you have the genotype Rr the flower color is ______________? – If you have the genotype rr the flower color is ______________?

Alleles Codominant – Dominant and recessive alleles are mixed – Red and white make ______________ Incomplete dominant – Dominant and recessive alleles are both seen – Red and white make ___________________

Alleles Sex linked – Found on the X or Y chromosome Males have a greater chance of having a disorder if the allele is on the X because they have only one Polygenic – Two more different genes work together to make a trait – Example: Eye color is determined by 3 genes Multiple Alleles – More than two types of alleles for a gene – Example: Blood groups (A B and O)

Central Concepts: Genes allow for the storage and transmission of genetic information. They are a set of instructions encoded in the nucleotide sequence of each organism. Genes code for the specific sequences of amino acids that comprise the proteins characteristic to that organism. 3.5Describe how Mendel’s laws of segregation and independent assortment can be observed through patterns of inheritance (e.g., dihybrid crosses). 3.6Use a Punnett Square to determine the probabilities for genotype and phenotype combinations in monohybrid crosses.

Mendel’s Laws Apply to Meiosis Law of Segregation – Chromosomes separate into different gametes Law of Independent Assortment – Chromosomes randomly separate – This helps create unique gametes with different combinations of alleles

Punnett Square Basics 1.Figure out what the parent alleles are 2.Place in parent alleles 3.Fill in the offspring alleles 4.Determine the genotype and phenotype possibilities Example: a tall parent has offspring with another tall parent. Each has a genotype of Tt.

GENOTYPES ¼ = _____ ½ = _____ ¼ = _____ Tt T t T TT T T t T tT t t tt t PHENOTYPES ____ or ____% _________ ____ or ____% _________ TT 75 Tt tt 3/4 1/4 SHORT TALL 25

Pedigree

Sex linked Pedigree