Review Session for Genetics and Human Heredity Unit 3 Central Dogma DNA RNA Protein Transcription information in DNA converted or copied into RNA This happens within the nucleus Translation RNA used for protein synthesis This happens in the ribosomes within the cytoplasm ribosome machinery for protein synthesis Nucleus Genomic DNA storage of genetic information S phase DNA replication prior to mitosis or meiosis Replication is making a DNA copy of DNA occurs during the S phase Transcription is making an RNA copy of certain parts In this class we don t have to worry about any distinction of different types of RNA DNA comes as a double helix A gene is only part of a chromosome So only part of the chromosome is transcribed into RNA DNA has bases of A C G and T RNA has A C G and U Every word is a three letter word called a codon Every gene is a different sequence of codons At the molecular level the DNA sequence is the same for all organisms In class we did a review question where we are given a few codons like AAA and a key saying what the names of those were You need to be able to use the key to understand the names of the codons listed Gregor Mendel used peas to experiment in genetics because there were easily identifiable phenotypes he could control the pollination and they reproduced quickly An allele that is masked is called recessive This was illustrated in Mendel s experiments where the alleles were unchanged not blended Like red and white flowers that didn t blend into pink but could create red or white offspring Because they don t separate Mendel proposed that they segregate not blend Remember an allele is an alternative form of the same gene They control the same trait Examples are red or white flowers They both control the color but they are just alternatives Looking at a pedigree it s important to remember that squares are men and circles are women Filled in circles are affected and demonstrate the phenotype whereas the unaffected are not filled in now we need to look at if it s inherited by autosomal x linked or y linked Then determine if it s dominant or recessive If it doesn t skip generations it s dominant It s autosomal if males and females are equally affected We can also look to see if the parents both the mother and father can pass it on Codominance and multiple alleles If there are more than 2 alleles ABO blood group is a good example An example of codominance is the blood type AB where A and B are both expressed equally and simultaneously AO is seen as A and BO is seen as B O is recessive because it s only demonstrated when it is homozygous OO Mitosis making 2 equal cells from one parent cell Meiosis making 4 cells with half of the genetic information from the parent This is used for making gametes In a human there are 46 chromosomes but either eggs or sperm have 23 chromosomes as they will join with that of the other parent
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