Life Science Chapters 4 Genetics

Gregor Mendel “father of genetics” experiments crossing pea plant traits a. Tall or short plants b. Round or wrinkled peas c. Yellow or green peas d. Smooth or pinched pods e. Green or yellow pod color

New Terms Gene: factor that controls a trait Allele: the different forms of a gene Purebred: always produces the same trait Hybrid: an organism w/ two different alleles for a trait – it is heterozygous Heredity: the passing of traits from parents to offspring Genetics: the scientific study of heredity

More Terms… Dominant allele: trait shows up in the organism when the allele is present, represented by a Capital letter ie “T” for tall Recessive allele: trait is masked or covered up, represented by a small case letter ie “t” for short

More Terms… Probability: A number that describes how likely an event will occur Punnett square: a chart that shows all possible combinations of alleles Phenotype: The outward visible trait being shown Genotype: The genetic makeup of the trait Homozygous: both alleles are the same for the trait in question Heterozygous: Alleles are different for the trait in questions

Punnett Square Way of predicting the possible phenotype & genotype outcomes when parents are crossed Must be able to determine the genotypes of the parents Bb Bb Bb Bb

Punnett Square Way of predicting the possible phenotype & genotype outcomes when parents are crossed Must be able to determine the genotypes of the parents In this case, when two hybrids are crossed, the possible outcomes are: the phenotype ratio is 3:1 3 dominant 1 Recessive genotype ratio is 1:2:1 1 Homozygus dominant 2 Heterozygus 1 Homozygus recessive

Reminder… Phenotype: The outward visible trait being shown Genotype: The genetic makeup of the trait Homozygous: both alleles are the same for the trait in question Heterozygous: Alleles are different for the trait in questions

Codominance: When both alleles are expressed in offspring Example: A white feathered chicken and a black feathered chicken make a black and white feathered chicken (both alleles are dominant) Anna’s Eyes???? 

Meiosis Meiosis is the process by which the number of chromosomes is reduced by h____ to form sex cells – spe___ and eggs. alf rm

Meiosis Meiosis I Meiosis II

Gamete (Sex Cell) Formation Normal chromosome # 23 pairs = 46 total Diploid – a cell that has both homologus chromosomes ( one from each parent) –2N Haploid – 1N - has only one of the homologus chromosomes (one from the father or the one from the mother) Egg & Sperm cells are haploid so when they combine during fertilization the zygote is once again diploid.

Two phases: Meiosis I and Meiosis II Before Meiosis 1. Every chromosome is copied 2. Centromeres hold the chromosomes pairs together Meiosis I A. The chromosome pairs line up in the center of the cell B. The pairs separate and move to opposite ends of the cell C. Two cells form each with only half of the original number of chromosomes

Meiosis II – The two new cells divide A. Chromosomes line up at the center of the cell B. Centromeres split and the chromatids separate and move to opposite ends of the cell End of Meiosis Four new cells are produced- 4 gametes (sex cells) - from the original parent cell. These 4 cells have only half the chromosomes of the parent cell. Each has only one chromosome from each original pair

Meiosis Parent cell – chromosome pair Chromosomes copied 1st division - pairs split 2nd division – produces 4 gamete cells with ½ the original no. of chromosomes

Mitosis vs. Meiosis Mitosis is cell division to produce new cells New cells are identical to the original cell Meiosis is cell division to produce sex cells New cells are not identical to the original cell

Meiosis Poster Project:

Human Genetics 23 pairs of homologus chromosomes in the human cell: 46 total chromosomes small sections of each chromosome, genes, are responsible for inheritance Chromosomes named as numbered pairs Pair 23 determines sex of individual Long chromosome X, short chromosome Y XX is Female, XY is Male

Sex Chromosomes The chromosomes that carry genes that determine the sex of offspring Eggs contain only the X chromosome Sperm contain an X or Y chromosome

Cells vs. Chromosomes Sex cells are eggs or sperm that contain ½ the number of chromosomes, including one sex chromosome Sex chromosomes contain genes that determine the gender of offspring

50:50 Chance Male sex chromosomes are XY Female sex chromosomes are XX

Sexual Reproduction Parent cells are known as sex cells or gametes Two parent cells join together to form a new individual Gametes (sex cells) have half the number of chromosomes in your body cells

Less is More Why is it important that sex cells have ½ the number of chromosomes? Ensure the newly formed offspring have the correct number of chromosomes (46)

Protein Synthesis osome Cells use information from a gene on a chrom_________ to produce a specific protein. osome

RNA Before protein synthesis can take place a “messe____” carry the genetic code from the DNA inside the nucleus into the cytoplasm. This genetic messenger is called ribonucleic acid or RNA nger

RNA

DNA vs RNA DNA RNA Copy One Strand Leaves the nucleus Master Copy Two Strands Never leave nucleus Copy One Strand Leaves the nucleus

Step 1 in Protein Synthesis Messenger RNA Production

Step 2 in Protein Synthesis Messenger RNA attaches to a Ribosome

Step 3 in Protein Synthesis Transfer RNA attaches to a Messenger RNA

Step 4 in Protein Synthesis Protein Grows http://www.learnerstv.com/animation/animation.php?ani=326&cat=biology https://www.youtube.com/watch?v=41_Ne5mS2ls

Chromosomes are made of DNA The Genetic code 19 Chromosomes are made of DNA A gene is a section of DNA that contains information for a trait/protein The sequence of bases in DNA forms the Genetic Code A group of three bases (a triplet) controls the production of a particular amino acid The different amino acids and the order in which they are joined up determines the sort of protein being produced

Valine Alanine For example Codes for Codes for 21 Cytosine Adenine Thymine Cytosine (C) Alanine Codes for Guanine (G) Adenine (A)

This is known as the triplet code 22 This is known as the triplet code Each triplet codes for a specific amino acid CGA - CAA - CCA - CCA - GCT - GGG - GAG - CCA - Ala Val Gly Gly Arg Pro Leu Gly The amino acids are joined together in the correct sequence to make part of a protein Although the DNA in the nucleus specifies the amino acids and their sequence, it is in the cytoplasm that the protein build-up takes place. The DNA of the nucleus makes a single strand of messenger RNA (ribo-nucleic acid) which leaves the nucleus and builds up the protein in the cytoplasm. The RNA code is complementary, but not identical, to the nuclear DNA. Text books usually give the coding for the RNA but in this presentation it is for the DNA itself Ala Val Gly Gly Arg Pro Leu Gly

A sequence of triplets in the DNA molecule may Genes 24 A sequence of triplets in the DNA molecule may code for a complete protein Such a sequence forms a gene There may be a thousand or more bases in one gene

How cells make proteins During protein synthesis, the cell uses information from a gene on a chromosome to produce a specific protein Protein synthesis takes place on the ribosomes in the cytoplasm of a cell

Role of RNA RNA (ribonucleic acid) carries the genetic code from the DNA inside the nucleus to the cytoplasm RNA is single stranded RNA contains adenine, guanine, cytosine and uracil (instead of thymine)

Types of RNA 1. Messenger RNA – copies the coded message from the DNA in the nucleus and carries the message to the ribosome in the cytoplasm 2. Transfer RNA – carries amino acids to the ribosome and adds them to the growing protein

Protein Synthesis 1. DNA molecule “unzips” between its base pairs. RNA bases match up along one of the DNA strands. The genetic information in the DNA is transferred to the messenger RNA strand.

2. Messenger RNA attaches to a ribosome and production of the protein chain begins 3. Transfer RNA attaches to the messenger RNA where they “read” the message in messenger RNA by matching up three letter codes of bases

4. Protein production continues until the ribosome reaches a three letter code that acts as a stop sign. The ribosome then releases the completed protein.

Protein Synthesis Overview The cell uses information from a gene on a chromosome to produce a specific protein

Mutation

Mutation nge tein type Mutation means “cha_____” in Latin Mutation can cause a cell to produce an incorrect pro____ during protein synthesis. As a result, the organism’s trait, or pheno____, may be different from what it normally would have been. nge tein type

Chp. 4 Review Jeopardy Games Full Chapter Review: https://jeopardylabs.com/play/genetics-and-heredity-7th-grade2 https://jeopardylabs.com/play/genetics333 Partial Review (Mainly Section 1&2, some 3): https://jeopardylabs.com/play/7th-grade-genetics https://www.superteachertools.net/jeopardyx/jeopardy-review-game-from-com.php?gamefile=http://www.superteachertools.com/jeopardy/usergames/Feb201108/jeopardy1298471734.txt#.VLLiL8ndNXs