Biopsychology Basic Genetics

Biopsychology Worksheet 3.1 – Basic Genetics 1. Every cell in the body contains ___23___ pairs of chromosomes (for a total of __46__ chromosomes), except for our ____gametes/sex/germ___ cells (____egg__ & ___sperm____), which only have one set of __23_ chromosomes. 2. Mendel’s Law of Segregation states that each person receives two alleles for each gene. One allele comes from the ____mom______ and the other comes from the ______dad_____. Each child receives only __1_ out of the ___2_ alleles that each parent could pass on to it. 3. True/False __T___ DNA molecules contain genes. __F_ Genes and chromosomes are the same thing. No, genes are found on DNA strands, and DNA strands make up chromosomes. __F___ The inheritance of one gene can not affect another inheritance of another gene under any circumstances. _F_ Every chromosome has the same number of genes. Larger chromosomes = more genes __T_ Each gene is essentially an instruction or blueprint for the body to create a certain protein. __F_ Chromosome pairs are paired up randomly. They are paired up and matched together (#10 from dad will match up with #10 from mom) 4. What is an allele? A specific type/form of gene Gene for eye color: Blue eye allele Brown eye allele Green eye allele 5. What is the difference between a genotype and a phenotype? Genotype = the actual genes/alleles that make up your chromosomes Phenotype = the physical/behavioral traits that are outcomes of you genotype (i.e., genotype = brown hair allele…phenotype = I have brown hurr) 6. Practice! Alleles: B (dominant) = brown eyes b (recessive) = blue eyes a. If a woman’s phenotype for eye color was blue, then what would her genotype be? bb homozygous recessive b. If that woman mated with a male who had a genotype of BB for eye color, what are the possible genotypes for their children be? (Draw a Punnett square to figure it out) (see picture) c. What are the different phenotypes that their children could have? 100% brown eyes d. What are the possible outcomes if that woman mates with a male who has a genotype of Bb instead? (see punnett square) 7. If I am a heterozygote for a trait, it means that my two alleles for that trait are __different (Bb)_. If I am a homozygote, my two alleles are _____the same (bb or BB)___. 8. I have the dominant allele that causes Huntington’s disease, but I am a heterozygote. I created offspring with someone who does not have Huntington’s disease. H = Huntington’s allele (dominant) h = normal allele (recessive) a) What is my genotype? Heterozygote = Hh b) What is my mate’s genotype? hh c) What are the chances that our child will have Huntington’s disease? (Punnett Square!) What does that mean? 50% 9. What is a locus? Location of a gene/allele on a chromosome 10. According to Mendel’s Law of Independent Assortment, genes for different traits are inherited ____separately/independently__. Just because I inherit one gene from dad, doesn’t mean I’m going to inherit another. We inherit them independently because of crossover and recombination that occurs in the Anaphase of Meiosis (when gametes are produced). 11. What is the exception to Mendel’s Law of Independent Assortment? Location – the closer in proximity the genes are to one another on a chromosome increases the odds that they will be inherited together. This process is called “linkage” 12. What factor increases the likelihood the genes will be inherited together? Close proximity/location on a chromosome. The closer they are together, the greater chance they will be linked/inherited together 13. Why does it make sense that our gametes only have 23 chromosomes, rather than 23 pairs? Because they divide and match up (mom’s and dad’s) evenly to make a whole set (23 pairs). So when zygote (fertilized egg when sperm and egg join) has a full set of 23 pairs. This is good for healthy offspring because inheriting 23 different chromosomes is going to provide more genetic variability. (t-shirt study – those who were more genetically different were rated as more attractive – genetic variability helps offspring survive – better immune systems, etc DNA notes: 3 nucleotide bases make up a codon One codon codes for one amino acid Many codons (which all code for one amino acid) make up polypeptide chains Polypeptide chain makes up a protein Many codons make up a gene/allele Protein synthesis: 1. MRNA slithers in and unzips DNA strand 2. In order to make copy of “coding” we look at “other strand, and make a copy (in this transcribed copy, U replaces T). 3. Once we finish copying all nucleotide bases and codons –mRNA doing transcription (happens in DNA strand), mRNA leaves the DNA (DNA zips back up) 4. mRNA carries the transcribed list of codons (our “ingredients) over to the ribosomes (in the soma and Endoplasmic Reticulum.) 5. Here, tRNA “reads” mRNA transcribed code, and it gathers all of the necessary amino acids and puts them together accordingly to make polypeptide chains/proteins. –tRNA gathering these amino acids together is called translation (happens in ribosomes).