GENETICS AND HEREDITY Chapter 5

Genetics and Heredity Heredity- the passing of traits from parents to offspring Genetics- the study of how traits are passed from parents to offspring

Gregor Mendel Considered the Father of Genetics Austrian Monk He studied pea plants because they have a wide variety of traits Pea plants also are readily available and have a relatively short life span He could also control pollination

Mendel Laws Law of Segregation- each allele separates from the other allele independently

Dominant and Recessive Dominant- a genetic factor that blocks another genetic factor  Only one copy of the gene is necessary for expression of the trait  “Stronger” Recessive- A genetic factor that is blocked by the presence of a dominant factor  Two copies of the trait are necessary for expression of the trait  Hidden, may appear to “skip generations”

Understanding inheritance Mendel concluded that one gene (factor) from each parent controlled each trait We know these factors to genes. Genes are located on chromosomes Humans have 46 total or 23 pairs 22 pairs are the autosomal chromosomes 23 pair determines the sex of the individual MaleXYFemale XX

Genes and alleles Gene- a section on a chromosome that has genetic information for a trait Allele- the different forms of a gene are called the alleles  R- for round r- wrinkled

Genotype and Phenotype Genotype- the genetic makeup The two alleles that control the phenotype of the triat Phenotype- the physical appearance How the trait appears or is expressed

Homozygous and Heterozygous Homozygous- when the two alleles of the gene are the same  RR, rr  Purebred Heterozygous- If the two alleles are different  Rr  Hybrid

Modeling inheritance Punnett square- a model used to predict genotypes and phenotypes of the offspring Pedigree- family tree showing the phenotype of the family members. Can be used to infer genotypes

Complex patterns of inheritance Incomplete dominance- some traits appear to be a combination of alleles A red flower camellia plant with a white flower camellia only produces pink flowers Codominance- When both alleles can be observed in the offspring  Cows- both red and white traits Multiple Alleles- More than two alleles for a trait  ABO blood groups Polygenic inheritance- a combination of many genes and usually some environmental factor (can be unknown)  Hair color, skin color, cleft lip, club foot

DNA and Genetics Genes provide the instruction or blueprint for making an organism DNA- organisms genetic material DNA codes for the genes DNA is tightly coiled It is a double helix structure or twisted ladder or zipper Discovered by Watson and Crick

DNA It is composed of three parts A sugar- deoxyribose A phosphate group A nitrogen base There are four common nitrogen bases Adenine- (A) pairs with Thymine (T) Cytosine (C) pairs with Guanine (G)

DNA replication Replication- process of copying a DNA molecule to make another DNA molecule 1. DNA strand separates and nitrogen bases are exposed 2. Nucleotides move in and form new nitrogen bases 3. Two new identical strands are made Almost like a zipper opening

Making proteins Made with the help of Ribonucleic acid (RNA) RNA is single stranded RNA has nitrogen base Uracil (U) rather than Thymine (T) Sugar is ribose Transcription- making mRNA (messenger RNA) from DNA

Translation The process of making proteins from RNA is called translation There are 2 other types of RNA  tRNA- transfer RNA  rRNA- ribosomal RNA  Translation  tRNA carries amino acids to the proteins  mRNA helps form chemical bonds that attach one amino acid to another  The first tRNA separates from its amino acid and mRNA.  The cycle continues.

Translating the RNA code The order of the nitrogen bases in the mRNA determines the order of the amino acids in the protein Three nitrogen bases are read to pick up the correct amino acid Three nitrogen bases= codon 64 codons but only 20 amino acids Some code for the same amino acid, some code for a stop, and some code for the beginning.

Mutations A mutation is a change in the nucleotide sequence of a gene Most mutations are corrected during replication Mutations can be triggered by X-rays, UV light, chemicals, and radioactive materials

Types of mutations Deletion- one or more nitrogen bases are left out of the DNA sequence Insertion- one or more nitrogen bases are added to the DNA Substitution- a nitrogen base is replaced by another different nitrogen base.

Results of mutations Not all mutations are harmful, some help an organism survive a change in environment Some will cause a genetic disease or disorder like cystic fibrosis or PKU.