Notes: Karyotypes, inheritance patterns, sex-linked, pedigrees 14.1: Human Heredity Notes: Karyotypes, inheritance patterns, sex-linked, pedigrees

Studying human heredity To understand human genetics, we look at the ENTIRE set of genetic information in a person Called a GENOME Scientists look at a picture of every chromosome, taken from a person’s nucleus Called a KARYOTYPE Diploid chromosomes are grouped in pairs, arranged by decreasing size

Types of Chromosomes Sex Chromosomes Autosomal Chromosomes 44 of 46 “Body” chromosomes Determines everything else, basically Majority of your traits are in autosomal chromosomes 2 of 46 in human genome Determine sex of individual Females have X X, males have X Y All female eggs have 1 X 50% of male sperm have 1 X, and 50% have 1 Y This is what makes having a boy versus having a girl, 50/50 probability

Genes on Sex Chromosomes 1200 genes are on the X chromosome 140 genes are on the Y, most of which deal with male sex determination and sperm development

Dominant & Recessive Alleles Humans, like pea plants, also follow “normal” dominant or recessive patterns Ex: Skin and hair color (darker colors are more dominant than lighter colors) Recessive – red hair (2 recessive alleles) Ex: Rhesus (Rh) factor- protein found in blood Rh+ is dominant, Rh- is recessive

Codominant & Multiple Alleles Many alleles show codominant inheritance Ex: blood type: IA , IB , i Type A – produces antigen A Type B – produces antigen B Type AB – produces both antigens (CODOMINANT) Type i (O) – produces no antigens

Blood Groups:

Sex-Linked Inheritance Genes found on X or Y chromosome show “sex-linked” inheritance patterns Genes on Y are ONLY found in males Genes on X are found in males/females, but show different patterns… hmm…….

For females to show recessive traits from X chromosome, BOTH chromosomes need to carry the recessive alleles If one X has a recessive, and one X has dominant, the trait will not appear Males only have 1 X, so if they inherit a recessive trait on it, they MUST show that trait since nothing can cover it up Sex-Linked

Human Pedigrees Show how traits flow through families Help determine the pattern in which traits are inherited (recessive, dominant, sex-linked)

Why we look somewhat like our parents, but not exactly. Human Chromosomes Why we look somewhat like our parents, but not exactly.

Everyone in the class is alike, but different. How are we alike Everyone in the class is alike, but different. How are we alike? How are we different?

The code for traits is contained in the nucleus of each cell of our body. Inside the nucleus are chromosomes which are made of DNA. This is the code to make you you. Cell Nucleus Chromosome DNA: One section of DNA is a gene

Chromosome smear

A karyotype is when chromosomes are grouped from largest to smallest. They are also grouped by the centromere position and the banding patterns.

Compare the karyotypes for a male and a female. A male karyotype A female karyotype

Body Cells Body cells are all cells in the body, except the egg and sperm Lung cells Liver cells Bone cells Nerve cells Skin cells Muscle cells, etc., etc., etc. Remember, every cell in the body has a set of chromosomes!!!

Before a body cell divides it copies every one of the chromosomes. When the body cell divides, each new body cell gets a copy of each chromosomes. The new body cell is exactly like the original cell!! They have the same number and same type of chromosomes.

Scientists are finding out more about DNA each day!!!!

Human Molecular Genetics This section explains how genetic engineering techniques are being used to study the genes and chromosomes in the human genome. It also describes how this information is used for gene therapy.

Human DNA Analysis Biologists search the volumes of the human genome using sequences of DNA bases

Human DNA Analysis Why might prospective parents decide to have genetic testing? Genetic tests can determine whether prospective parents risk passing alleles for genetic disorders to their children

DNA FINGERPRINTING What is DNA fingerprinting? It is the identification of individuals by a method that analyzes sections of DNA that have little or no known function but vary widely from one individual to another.

The Human Genome Project What is the Human Genome Project? It is an ongoing effort to analyze the human DNA sequence.

Human Genome Project The mRNA coding regions of most genes are interrupted by Introns.

Human Genome Project List three other parts of the gene that researchers look for. Promoter “Start” site for transcription “Stop” site for transcription

Human Genome Project Why are biotechnology companies interested in genetic information? They are trying to use this information to develop new drugs and treatments for diseases.

Gene Therapy In gene therapy, an absent or faulty gene is replaced by a normal, working gene.

Gene Therapy Have all gene therapy experiments been successful? No Attempts to treat cystic fibrosis by spraying genetically engineered viruses into breathing passages have not produced a lasting cure.

Gene Therapy Ethics Ethical Issues in Human Genetics What other changes could be made to the human genome by manipulating human cells? Biologists could try to engineer taller people or change eye color, hair texture, sex, blood group, or appearance. They could even clone human beings.

Gene Therapy Ethics The goal of biology… Is to gain a better understanding of the nature of life.

Just for thought….. Should Scientists be expected to make all ethical decisions regarding advances in human genetics???