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Topic 3 Genetics Genetics is the science of how _______ information is passed on from one generation to the next, using the DNA in _______. 3.1 Genes • A gene is a _________ factor that consists of a length of DNA and influences a specific ______________. • Heritable means passed from ________ to offspring, characteristic means a _____, like eye or hair color. • Humans have an estimated ________ genes, organized into chromosomes. Where genes are located • A gene, for a particular trait, is always located at a specific spot called its ______ (plural ____). • Scientists are mapping the loci of all the genes. • Scientists know that the gene for making the protein _________ is located on chromosome 1. • If you have the mutated version, you can’t see in _____. There is only a single base difference. Alleles • Variations or versions of a gene. Usually different by only a few _____ pairs. • While there are different alleles, they are always located at the some ______ on everyone's DNA. • Example: _______________is a inherited disease causes by a mutated gene on chromosome 7. • The normal allele produces the correct amount of ______ in your body, the mutated allele produced too much. Base changes • Just one base change can create a _________ that causes disease. • Another example is a gene that determines the type of ear wax you have (_________). There are two versions (alleles) of this gene (chromosome 16), one causing dry ear wax and the other causing wax that is more fluid. • Wet earwax is more common in __________ and ________, dry more common in _______ • This gene also is involved in the production of ______ ______with a possible link to breast cancer. • Different versions of genes, alleles, are created by mutation. • ________ _______disease is a good example. Mutations • A random, rare change in genetic material. • A ____________ mutation would involve a wrong base being substituted for the correct one, like in sickle cell disease. • Some mutations are _____. There is a mutation that prevents people who have it from being able to become infected by the ____ _______. • Whether a mutation is good, bad or neutral depends on what they are AND the __________. • The gene that allows people to digest _______ is a mutation. • Believed to have originated in ________, so most Europeans and North Americans are not lactose intolerant. • Gene therapy involves putting a ______ gene into someone who needs it. Dangerous, ethical issues. Sickle cell disease • Caused by a single base substitution mutation. • The gene is responsible for making the protein _____________. • The mutation causes the hemoglobin protein to have a different ______, causing the red blood cells it is located in to also have a different shape. • Instead of _________ _____, valine is added to the chain. _________ can’t be carried as efficiently, the cell shape causes _______. Sickle cell disease • If the 2 _______ you have are both normal, you have normal hemoglobin and normal shaped red blood cells. • If the 2 _______ you have are both the bad ones, you have sickle cell disease. • If you have one of each, you are said to have the sickle cell ______ and do show some signs of the disease but not nearly as severe. • Having one or two sickle cell alleles prevents ________. Genome • The complete set of a organism’s base sequences. In humans, about ________bases. • Some organisms have been completely sequenced, fruit fly and E. coli. • How do geneticists figure out a genome? • _______Sanger Technique – DNA samples are chopped into pieces, and copies are made (PCR) • _________ added to start replication • Each piece is put into DNA polymerase and the 4 nucleotides so that replication can occur • Each time, a special tagged _____base is tested which, if added to the chain, will _____ replication. • The pieces will all end with the tagged nucleotide and all the pieces are run through ____ ______________. Human Genome Project • Began trying to sequence the human genome in _____. • In _____, they announced they had sequenced the entire human genome. • They are now working on what each gene does. As this happens, scientists know the _____ of individual genes and what they do. • Before the Project, they knew where fewer than ____ genes were that caused disease, they now know ______1400. • Information learned from the Human genome project can help scientists study __________ patterns and how we _________migrated over the past. • If we know where the genes are for making a certain protein, we can then use that gene in the lab to make molecules for people who can’t make them due to genetic abnormalities. • Carl ______ – Studying mutations in genes discovered ____________ • You can’t _________ a gene 3.2 Chromosomes • Because prokaryotes reproduce by binary fission, they have only ____ chromosome • Organisms that reproduce ________ will have two of every chromosome because the organism would get them from each ______. • Some prokaryotes and archaea have a ________, eukaryotes don’t. • Plasmids can ___________ independently Eukaryote Chromosomes • Chromosomes are made of ____ which is the genetic material of the cell. • The DNA is wrapped ______ around 8 histone proteins (2 each of 4 diff types) forming an area called a __________. Sometimes a ninth histone • The DNA is attracted to the histones because DNA has a ________ charge and the histones have a _________ charge. • The areas of nucleosomes won’t __________ so the nucleosomes help to _________ the transcription process. Multiple Chromosomes • Eukaryotes have more than one chromosome (usually), and there will always be ____ of each one. • Humans have ___ chromosomes, 2 sets of 23. • We get a set of 23 from each parent so we have 2 number one chromosomes, 2 number two chromosomes, etc. • These sets of two are called __________ chromosomes. The #1 from mom and the #1 from dad are homologous. Homologous Chromosomes • Same genes in the same locus (loci), but not necessarily the same _______. • _______ is a term used to describe a cell that has 2 of each chromosome. Most cells in our body are diploid. (46 chromosomes) • ________ is a term used to describe a cell that only has 1 of each chromosome, the sex cells or _________. (23 chromosomes) • __ represents the haploid number and ___ the diploid number • Chromosome number is a defining feature of a ________. • _____ cells in a species can be different (n). • Some individuals can be born with less or more (_________________) • Some cells don’t have any chromosomes, like ____ _________cells. Karyogram/Karyotype • A karyotype is the specific number and appearance of the ___________ of an individual. • A karyogram is a ________ of the chromosomes. Steps for making a karyogram • Cells are _______ and put on a slide to look at under a microscope • A ________ is taken of a cell in __________ • Chromosomes are cut/pasted into order by _____, largest to smallest, and position of ____________. • Exception is the 2 ____ chromosomes which are shown ______. Sex Determination • The sex chromosomes are X and Y. • The X is _______ and contains many more genes • Unlike the other 22 pairs, the sex chromosomes can be very different. • XX = ________ (physically) - gametes will all be X • XY = _____(physically) - gametes will be X and Y • ______ determines sex of child • Any chromosome that is NOT a sex chromosome is called an ____________. • Humans have 22 pairs of autosomes and one pair of sex chromosomes. (normally) • Traits described as autosomal would have their genes on one of the 22 pairs of autosomal chromosomes. • Traits described as _________would have their genes on one or both of the 2 sex chromosomes. Autoradiography • X-rays use __________ to create an image of an object. • Autoradiography uses radioactivity being _____ _____by an object to create an image. • Can be used to get images of DNA so its _______ can be measured. • ________technique uses radioactive material called radio markers. Radioactive form of ________ using 3H • In 1962 used to prove bacteria DNA is a loop 3.3 Meiosis • _______ have only one set of chromosomes (n). That way, when an egg and a sperm combine, you get 46 (2n). • Meiosis is the process where a _______ cell (2n), creates 4 ________ gametes (n). • ________ is 46 (2n) nucleus creating two 46 (2n) nuclei. • _______ is 46 (2n) nucleus creating four 23 (n) _________ cells • DNA is _________ prior to meiosis, so each of the 46 chromosomes looks like an x , two sister ___________ connected by the centromeres. • The parent cell must divide ______ during meiosis, the first division creating 2 cells that are ________ (n). • The second division seeing the 2 haploid each divide into 4 _________. Crossing Over • During the _____ division of meiosis, the ____________ chromosomes pair up side by side. • Crossing over allows the mothers DNA to mix with the fathers DNA • This increases _________ within the gametes • The new chromatids are called ____________ chromatids. Random Orientation • During __________ of the first division, the homologous chromosomes are going to line up, ______________in the middle of the cell. • How they line up is _______. • This also increases variation within the gametes Division I Prophase I • Chromosomes _____ and become visible • _________ membrane begins to break down • Spindle fibers form, __________ disappears These steps are exactly the same as __________ • ____________ chromosomes are attracted to each other. • ________ _______occurs Division I Metaphase I • Homologous chromosomes line up along the _________ by ________ orientation. • Nuclear membrane is gone • ________ _________grow toward the chromosomes Division I Anaphase I • Spindle fibers attach to ____________ of chromosomes and pull them toward the ______. Telophase I • Spindle fibers ____________. • Chromosomes _______, nuclear membranes form. • Many ________ don’t have Telophase I • ___________ occurs and created 2 haploid (n) cells Division II • Basically this is ___________ • Prophase II DNA condenses into visible chromosomes Spindle fibers are produced, nucleolus disappears. • Metaphase II Nuclear membrane gone ____________ chromosomes line up ___________ on the equator Spindle fibers attach to the ____________ Division II • Anaphase II Centromeres split and ______ ____________move toward the poles. In animals, cell membrane begins to ______ in, in plants, cell _______ begin to form • Telophase Chromosomes unwind, nuclear membranes form. Fertilization and variation • Crossing over during ___________and random orientation during Metaphase I create ___________ among gametes. • ______ ___________also creates variation because of which of the different sperm cells ______________ the egg cell. • The number of different gametes a human could produce is _____ or 8,388,608. That doesn’t include _________ _______. Extra or missing Chromosomes • Sometimes organisms end up with less or more chromosomes than normal. • Example in humans is _____ ___________, where a child is born with ___ chromosomes instead of 46 because they have an _________. • Caused by ________________, usually during Anaphase I. • Causes some eggs to have 2 #21 chromosomes and others to not have any. • Studies of families with children who have Down Syndrome (________________ studies) show that the _____ of the mother shows the highest correlation. • The older the mother is, especially after ___, the greater the odds. • A ____________ will show whether a child has a chromosome issue or not. Obtaining Cells for Karyotyping unborn • Two different procedures • ________________ uses a needle to extract amniotic fluid which will contain cells • _________ ______ __________obtains cells from the placenta’s finger-like projections called villi • In both cases, the fetal cells are grown in the lab and a karyotype is created.