HEA1091 Introduction to genetics annotated 2023 (1).pptx

OFFICI AL Introduction to Genetics HEA1091 OFFICI AL DNA Animations video OFFICI AL Learning outcomes By the end of this session you will be able to… Describe DNA and RNA Describe protein synthesis Describe nuclear cell division Define inheritance Give three examples of genetic conditions vevox.app...

OFFICI AL Introduction to Genetics HEA1091 OFFICI AL DNA Animations video OFFICI AL Learning outcomes By the end of this session you will be able to… Describe DNA and RNA Describe protein synthesis Describe nuclear cell division Define inheritance Give three examples of genetic conditions vevox.app 126-027-607 OFFICI AL The cell vevox.app 126-027-607 The nucleus OFFICI AL Deoxyribonucleic acid (DNA) vevox.app 126-027-607 OFFICI AL Ribonucleic acid (RNA) Short single strand ‘Copy’ of a gene in the nucleus Instructions to the cytosol To build proteins vevox.app 126-027-607 Uracil (U) instead of thymine OFFICI AL Chromatin and chromosomes Genes are arranged along chromosomes Human somatic (body) cells have 46 chromosomes 23 inherited from each parent Each chromosome is a long DNA molecule coiled with proteins and some RNA This complex is called chromatin When cells are not dividing – diffuse mass Wrapped around histones – organise coiling & folding Just before division – DNA replicates Condenses forming a pair of chromatids vevox.app A pair of chromatids is a chromosome 126-027-607 OFFICI AL Protein synthesis 20 amino acids Peptide bonds Polypeptide chains Folds into a complex and intricate shape Shape determines the function! vevox.app 126-027-607 OFFICI AL Functions of proteins include… Plasma membrane of cells Cytoskeleton Other organelles Hormones Antibodies Contractile parts of muscle Enzymes (regulating chemical reactions) Transporters (of substances in the blood) vevox.app 126-027-607 Proteins determine physical and chemical characteristics of cells, and, therefore, the organisms formed of them OFFICI AL How does DNA and RNA carry information? In DNA – sets of 3 nucleotides In RNA – complementary sequence of 3 nucleotides called a codon Which codes for a specific amino acid vevox.app 126-027-607 How do you get from gene to protein? 1.Gene (DNA) 2.Transcription 3.RNA 4.Translation 5.Protein OFFICI AL Protein synthesis - Transcription In the nucleus RNA polymerase attaches Start and stop instructions Pre-mRNA Exons – sections that code the protein Introns removed by snRNPs or “snurps” vevox.app 126-027-607 mRNA passes through a pore Into cytoplasm OFFICI AL Three different RNA molecules are transcribed mRNA vevox.app 126-027-607 rRNA tRN A OFFICI AL Protein synthesis - Translation mRNA binds to ribosome 1st tRNA binds to start codon 2nd tRNA binds to the next codon Amino acid on the 1st tRNA binds with the 2nd mRNA moves along 1 codon Process continues Until stop codon reached vevox.app 126-027-607 Polypeptide chain OFFICI AL From gene to protein vevox.app 126-027-607 OFFICI AL From DNA to Protein video OFFICI AL Epigenetics How does each cell express only the genes it needs for its identity and function? vevox.app 126-027-607 Epigenetics is the chemical process of turning genes on or off, without changing the sequence Tissue identity – maintained through cell division Disease – epigenetic errors Environment – diet, pollutants Active chromatin – loosely arranged Inactive chromatin – tightly packed Histone tails can be tagged DNA tightens, unwinds, or a histone can be moved Methylation and acetylation OFFICI AL Cell death vevox.app 126-027-607 Apoptosis Necrosis Genetically programmed Not programmed Phagocytosis Trauma, disease, pathology Minimal damage Cell lysis and spilling of contents OFFICI AL Cell division Somatic cell Somatic cell division (mitosis) replaces dead or injured cells, and adds new ones during growth Producing 2 genetically identical diploid (2n) cells – 2 sets of chromosomes 23 pairs 46 in total Germ cell (gamete) What if reproductive cells had 46 chromosomes? When they merge at fertilization, there would be 92!! Germ cells have 23 single chromosomes Reproductive cell division (meiosis) produces haploid (n) cells that are not genetically identical vevox.app 126-027-607 OFFICI AL Somatic cell division vevox.app 126-027-607 OFFICI AL DNA replication 2 strands uncoil Separate at the hydrogen bonds (base pairs split) Exposed base of old DNA pairs with a new nucleotide 2 strands become 2 new identical double helix DNA molecules vevox.app 126-027-607 OFFICI AL Somatic cell nuclear division (mitosis) vevox.app 126-027-607 OFFICI AL Mitosis and the Cell Cycle video OFFICI AL Telomeres and aging Jeanne Calment, 1875 – 1997 (allegedly) vevox.app 126-027-607 OFFICI AL Cell death vevox.app 126-027-607 Apoptosis Necrosis Genetically programmed Not programmed Phagocytosis Trauma, disease, pathology Minimal damage Cell lysis and spilling of contents OFFICI AL Reproductive cell division (meiosis) Prevents number of chromosomes doubling at fertilization Allows for exchange of genetic material Occurs in ovaries and testes Starts with a germ line cell (2n) DNA replicates Meiosis I: halves the number of chromosomes Gene exchange occurs in Prophase I Meiosis II: the sister chromatids are split End with 4 haploid (n) cells vevox.app 126-027-607 OFFICI AL How Meiosis Works video OFFICI AL Meiosis Animation video OFFICI AL Inheritance The passage of hereditary traits from one generation to the next. It is the process by which you acquire your characteristics from your parents and may transmit some of your traits to your children. vevox.app 126-027-607 OFFICI AL Genotype 1 chromosome in each pair from mother 1 from father Each has genes that control the same traits (homologous) If there is a gene for a particular trait on one There will be an alternative gene for the same trait in the same position on the other (called an allele) Consider allele, P, that codes for an enzyme, and dominates Mutated allele, p, fails to produce the enzyme, and is masked The genotypes are the possible vevox.app combinations of these different genes that 126-027-607 can combine by the union of sperm and ova OFFICI AL Phenotype A person with Pp has a different genotype from a person with PP But P is dominant and will be expressed over p Both will not have the disease They have the same phenotype The phenotype is how the genetic combinations are expressed in the body People who carry a recessive gene but don’t express it can pass it to their offspring They are carriers vevox.app 126-027-607 OFFICI AL Dominant-recessive inheritance Most inheritance patterns don’t follow simple dominantrecessive. Phenotype can be affected by: Environment (folate deficiency in pregnancy) Other genes – complex inheritance (skin/hair/eye colour) Some genes have two alternative forms – multiple allele inheritance, e.g. blood group inheritance, producing 4 blood types (A, B, AB, and O) Or if neither pair is dominant over the other there can be incomplete dominance. In sickle cell disease, PP forms normal haemoglobin, pp has severe disease, Pp minor anaemia vevox.app 126-027-607 problems OFFICI AL Sickle cell disease (incomplete dominance) vevox.app 126-027-607 OFFICI AL Sickle cell crisis Triggers: acidosis, dehydration, cold, exercise, stress, infection Can damage organs – heart, spleen, kidneys, lungs Severe persistent pain in skeleton, chest, and/or abdomen Swollen hands and feet (dactylitis) High temperature, lethargy, breathlessness 8% of black population carry the gene Affects 1 in 2000 vevox.app Protective 126-027-607 against malaria OFFICI AL Sex determination Sex chromosomes determine the sex of the offspring Also determine other traits Many genes for these traits are present on X But absent on Y Inheritance of these traits is sex-linked vevox.app 126-027-607 OFFICI AL Red-green colour blindness (sex-linked inheritance) Normal male Condition caused by a recessive gene –a The normal gene is dominant – A Female carrier OFFICI AL Congenital haemophilia Same X-linked recessive inheritance Exclusively boys/men Mutations in genes that express clotting factors VIII and IX Located on long arm of X chromosome When clotting factors are not produced, normal clotting is impaired Spontaneous or trauma-induced bleeding in joints and muscles Bleeding after surgery Gastrointestinal bleeding or haematuria Easy bruising and recurrent nasal bleeding Factor VIII or IX replacement Pain medication Antifibrinolytic agents Bleeding prevention, education, physiotherapy vevox.app 126-027-607 OFFICI AL Nondisjunction Error in cell division during meiosis Uneven split of chromosomes The cell is aneuploid Most cases of Down’s syndrome are aneuploid (2n + 1) A genetic condition But not strictly heritable vevox.app 126-027-607 OFFICI AL Down’s syndrome 95% caused by nondisjunction Of which 95% have standard trisomy of chromosome 21 Biggest risk factor – advanced maternal age Characteristic facial features Degree of intellectual disability and behavioural difficulties Hypotonia Congenital heart disease Motor delay Hearing loss Autism spectrum disorder Constipation Life expectancy 50 – 60 years, and vevox.app continuing to improve 126-027-607 OFFICI AL DNA Animations video OFFICI AL Additional resources Transcription and Translation Overview Epigenetics – An Introduction Cell Cycle (Mitosis) Huntington’s article The Language of Genetics – an ebook in the HEA1093 reading list Human Nature – a documentary about genetic engineering and CRISPR Originally delivered by Mark Vann [email protected] vevox.app 126-027-607 OFFICI AL Learning outcomes It is the end of the session, you are now able to… Describe DNA and RNA Describe protein synthesis Describe nuclear cell division Define inheritance Give three examples of genetic conditions vevox.app 126-027-607