Y8 Genetics PDF

Y8 Genetics Species A species is a group of organisms that can reproduce with one another to produce offspring that can also reproduce. Variation Definition: Differences between individuals of the same species. Inherited Variation Environ...

Y8 Genetics Species A species is a group of organisms that can reproduce with one another to produce offspring that can also reproduce. Variation Definition: Differences between individuals of the same species. Inherited Variation Environmental Variation Continuous Variation Discontinuous Variation Inherited vs. Environmental Variation Inherited Environmental Inherited and Environmental Variation Characteristics that are passed on to us from our parents are inherited characteristics. Characteristics or features in an organism that are not inherited are called environmental characteristics. Many characteristics are a combination of inheritance and environment. Combination of inheritance and environment ?? Our Inheritance Heterochromi a Difference in melanin distribution Discontinuous and Continuous variation Discontinuous variation is based on features that cannot be measured across a complete range. Example: eye colour, male or female, blood group etc. In continuous variation there is a complete range of measurements from one extreme to the other Example: height, weight, wing span, milk yield in cows  The following are possible discontinuous variations! - Colour blindness - Wet or Dry earwax - Number of fingers  Discontinuous Variation Human Traits YES % NO % A Dimples B Widow’s Peak C Detached Earlobe D Tongue Rolling E Longer 2nd Toe F Straight Thumb G Bent Pinky H Mid-digit Hair I left handedness  YES NO A Dimples ( 酒渦 ) Variation B Widow’s Peak ( 美人啄 )  YES NO C Detached Earlobe D Tongue Rolling ( 卷舌 ) E Longer 2nd Toe 二腳趾長過腳趾公  YES NO F Straight Thumb 直拇指 G Bent Pinky 曲尾指 H Mid-digit Hair 手指中段毛 I Left handedness 左手 Continuous Variation VS Discontinuous Variation https://www.youtube.com/watch?v=xX93td7hkDM Continuous Variation Discontinuous Variation Continuous vs. Discontinuous Our Inheritance Characteris tics: Black Eye color Brown Hair color Red Blood type Blond Earlobe Height Weight 184cm 172cm 169cm 166cm 177cm 175cm Which of the following variations are… 1. Environmental variation / Genetic (inherited) variation/Both ? 2. Continuous variation/ Discontinuous variation? Variation Read Biology textbook Chapter 5.1-5.2 (page 68-70) Introduction to Gene Genes and Chromosomes Introduction to Gene (What is Gene?) Genes and Chromosomes Introduction to Gene (Where do your Genes come from?) Level of organization in Gene Level of organization in Gene (From larger to smaller) Cell  Nucleus  Chromosome  DNA  Gene What are chromosomes? Chromosomes are long strands of genetic information located in the nuclei of cells. Chromosomes are DNA wrapped around a protein. Why? Chromosomes are most visible during cell division when they replicate and look like this… You will see chromosomes represented in both ways. 9A With love from Mum and Dad From our mother and father You are similar to both your mother and your father. But why? ovum (egg) from your mother 23 chromosomes sperm from your father 23 chromosomes Homologous chromosomes In most cells, chromosomes are matched in pairs based on their size and shape. chromosome from chromosome from female parent male parent homologous chromosomes Matching pairs of chromosomes are called homologous chromosomes. Where do homologous chromosomes come from? Each pair of homologous chromosomes contains one chromosome that has been inherited from each parent. Human chromosomes In human body cells (except sex cells) there are a total of 46 chromosomes. How many pairs of homologous chromosomes are there in human body cells? 23 pairs of chromosomes You inherit half your chromosomes from your mother and half from your father. How many chromosomes do you inherit from each parent? 23 unpaired chromosomes  Summary Remember, Science is about drawing theory from what we can observe. It must be evidence-based. What we observed Theory/ analysis/ categorization Different variations between human Genes (alleles) There are long strands inside nucleus We call them DNA There are DNA and proteins in Proteins are like ‘blu tac’ that can make chromosomes the long strands of DNA condensed Human has 46 chromosomes in most cell The theory of evolution Sex cells has only 23 chromosomes Reason: 23 (sperm) + 23 (egg) = 46 The cell division process to form sex cells is The process of cell division: Meiosis and different from other cells. For the production mitosis of sex cells, chromosomes have to be lined up in pairs before they divide. Those 46 chromosomes are found that: Half The 23 pairs are chemically stained and from the sperm (father), categorized digitally from large to small half from the egg (mother) (except from the sex chromosomes) in Karyotype. A karyotype is a diagram of a complete set of chromosomes. Are all chromosomes all the same size and shape? - No! How many are there? X and Y chromosomes There are two types of sex chromosome with names that are very easy to remember! X chromosome Y chromosome Females have two X chromosomes, one from each parent. XX Males have one X chromosome and one Y chromosome. Which parent does a baby boy inherit his Y chromosome from? XY X and Y chromosomes Does this set of chromosomes come from a male or female? 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 XY 21 22 23 What kind of sex chromosomes are there in this person’s sex cells? Male or Female? This is a MALE Karyotype. (XY) Seen from chromosome 23, aka Sex chromosome So, how does a Female sex chromosome (XX) looks like?  Chromosomal Disorder A chromosomal disorder results from a change in the number or structure of Observable chromosomes. traits Example 1 a person born with an extra copy of chromosome 21  Chromosomal Disorder Example 2 affects only females, results when one of the X chromosomes (sex chromosomes) is missing or partially missing.  Chromosomal Disorder Example 3 Klinefelter Syndrome a male born with an extra X chromosome  Summary Remember, Science is about drawing theory from what we can observe. It must be evidence-based. What we observed Theory/ analysis/ categorization Different variations between human Genes (alleles) There are long strands inside nucleus We call them chromosomes There are DNA and proteins in Proteins are like ‘blu tac’ that can make chromosomes the long strands of DNA condensed Human has 46 chromosomes in most cell The theory of evolution Sex cells has only 23 chromosomes Reason: 23 (sperm) + 23 (egg) = 46 The cell division process to form sex cells is The process of cell division: Meiosis and different from other cells. For the production mitosis of sex cells, chromosomes have to be lined up in pairs before they divide. Those 46 chromosomes are found that: Half The 23 pairs are chemically stained and from the sperm (father), categorized digitally from large to small half from the mother (mother) (except from the sex chromosomes) in Karyotype. XX female; XY male a change in the number or structure of Lacking or excess of chromosomes chromosomes would result in chromosomal would also lead to rearrangement of disorder chromosomes Short Summary 1. What does the following terms means? a) Karyotype b) Chromosome 1 a) A diagram of a complete set of chromosomes. b) Chromosomes are long strands of genetic information located in the nuclei of cells. 2. How many chromosomes does a Down syndrome person’s normal cell have? 2) 47 chromosomes Why are mules infertile? Chromosome Chromosome No. = 64 No. = 62 Chromosome No. = 63 Tigon (38 chromosomes) Liger (38 chromosomes) = = Tiger, dad (38 chr.) + Lion, mum (38 chr.) Lion, dad (38 chr.) + Tiger, mum (38 chr.) Although liger and tigon have even no. of chromosomes, chromosomes of tiger and lion are not 100% compatible. Therefore, liger or tigon are infertile. Gene & Chromosome Read Biology textbook Chapter 17.2- 17.3 (Page 210-213) A karyotype is a diagram of a complete set of chromosome. If you observe the homologous chromosomes closely, you will find that they are not the same. Why?  Do these two pea flowers have the same gene that code for color? Allele Same gene that codes for color, but because it has different versions, it can code for different colors. Allele = different versions of genes This is a pair of chromosomes 😉  Alleles The chromosomes in a pair carry the same genes in the same places. But there are different versions of the same gene. Different versions of the same gene are called alleles. Our Inheritance Allele: specific variation or characteristic that is located on a gene (eg. eye color, carrier of cystic fibrosis) Dominant: characteristic which is inherited from mother or father that is stronger and is expressed in the offspring Recessive: characteristic which is inherited from mother or father that is weaker and is not expressed in the offspring if a Some alleles are dominant while others are recessive. Why??? 😨  Homozygous Vs Heterozygous ▪ If both the alleles are the same, the organism is homozygous for the trait. ▪ If the alleles are different, the organism is heterozygous for that trait. Any letter!!!! UPPER CASE – dominant LOWER CASE – recessive dominant Genotype: Bb BB bb Our Inheritance B (brown eye color) b (blue eye color) Homozygous: characteristics from mother and father that are the same eg. BB (homozygous dominant), bb (homozygous recessive) Heterozygous: characteristics from mother and father that are not the same Our Inheritance Genotype: The alleles combination of a gene. eg. BB, Bb, bb (use letters to express the alleles combination) Phenotype: The expression of the gene. eg. Brown eye color, Blue eye color (describe the observable traits or  Recessive vs Dominant A recessive allele only shows if an individual has two copies of it. Example: The allele for blue eye colour is recessive. You need two copies of it to have blue eyes. bb A dominant allele always show even if the individual has only one copy of it. Example: The allele for brown eyes is dominant and so you will have brown eyes if you have one copy of it. You will have brown eyes if you have two copies of it. Bb bB BB  Punnett square The Punnett square is a diagram showing the possible combinations of genes, based on the genes of parents. It is used to predict the outcome of a particular cross or breeding experiment. 1 min Discussion From a biological perspective, should women be blamed for not giving birth to a boy? Calico cats are predominantly female. Why? https://www.punnettssquare.com/2015/09/why-are-calico-cat-predominantly-female.html 5 mins Discussion Preimplantation genetic screening (PGS) Can you explain? Given: parents pass down the genes for red-green colour vision deficiency through the X chromosome red-green colour vision deficiency is recessive Father: Normal (XY) Mother: Carrier (X’X) Some alleles are dominant while others are recessive. Why??? 😨 Our Inheritance Y = yellow y = green 1) What is the Genotype for individual A, B and C? 2) Give the description of the genotypes. 3) What is the Phenotype for individual A, B and C Cystic fibrosis Cystic fibrosis (CF) is a genetic disorder that affects mostly the lungs, but also the pancreas, liver, kidneys, and intestine. Cystic Fibrosis (recessive allele) If both parents are carriers of the recessive allele for a disorder, all of their children will face the following odds of inheriting it: 25 % chance of having the recessive disorder 50 % chance of being a healthy carrier but has recessive allele  Cystic fibrosis If both mother and father are the carriers for cystic fibrosis. a) What are the chances to have a baby with cystic fibrosis? b) What are the chances to have a baby who is a carrier for cystic fibrosis?  Cystic fibrosis If only mother is the carrier for cystic fibrosis and father is normal. a) What are the chances to have a baby with cystic fibrosis? b) What are the chances to have a baby who is a carrier for cystic fibrosis? Pedigree Chart The pedigree chart is a chart used to illustrate a particular trait in a family. - Square represents male and circle represents female. - The shaded individuals are those with that trait. Pedigree chart symbols Exercise recessive trait The following pedigree chart shows cystic fibrosis disease in a family. 1) State the phenotype for individual 2. 2) Deduce the genotype for individual 8 and 9. 3) If individual 14 is marrying to a cystic fibrosis patient, what are the chances of their children getting cystic fibrosis?