Heredity, Inheritance, and Variation PDF

HEREDITY, INHERITAN CE, and VARIATION  Similarities and Differences Among Organisms People have always been fascinated with the way children resemble their parents.  Similarities and Differences Among Organisms The passing on of traits from parents to offspring is explained by heredi...

HEREDITY, INHERITAN CE, and VARIATION  Similarities and Differences Among Organisms People have always been fascinated with the way children resemble their parents.  Similarities and Differences Among Organisms The passing on of traits from parents to offspring is explained by heredity. Genetics – is the science that deals with the study of heredity.  Gregor Mendel – he is now called “The Father of Genetics” He was remembered as a gentleman who loved flowers and kept extensive records of weather and stars when he died.  Similarities and Differences Among Organisms Nature versus Nurture o Humans grow and develop according to the instructions in their genes. o Separate relative influence of heredity and environment on an individual’s characteristics.  Similarities and Differences Among Organisms The environment may influence the growth and development of an individual. A person may not have the perfect combination of genes for intelligence, but if the environment motivates and nurtures learning, the person may develop a higher intelligence quotient.  DNA, Genes, Chromosome and Traits Traits are observable characteristics determined by genes. Genes refer to a specific segment of a deoxyribonucleic acid (DNA). Genes store the information needed to make the necessary proteins that will code for specific traits.  DNA, Genes, Chromosome and Traits DNA is a double helix molecule composed of thin strands arranged like a twisted ladder found inside a It contains the instructions chromosome.for the development and “blueprint of life”function of all living organisms hereditary materials  DNA, Genes, Chromosome and Traits DNA molecules make up the chromosomes found inside the nucleus of the cell. The complex molecule is made up of four nucleotide bases - adenine (A), guanine (G), cytosine (C), and thymine (T) - that are arranged in a specific sequence to form genes. These genes encode the information needed for cells to grow, divide, and perform their specific functions.  DNA, Genes, Chromosome and Traits Chromosomes – thread-like structure - “histones” – supports the structure of the DNA Each chromosome has a constriction point called centromere. Explains the relationship between the chromosome, DNA, and genes. Here DNA (Deoxyribonucleic Acid): C Cell: composed The image ofontightly the left startsstrand coiled with the cell. andEach cell ingenetic transmits the body contain instruction form of a double helix (illustrated Nucleus: Inside the cell, the nucleus image). center and contains the chromosome Gene: A gene is a segment of D Chromosome: Chromosomes are str instructions to make proteins, wh within the nucleus. They are made up variety of functions in the body. I proteins. Chromosomes carry genetic labeled as specific segments of passed from one generation to the ne The right side of the image repe how the cell contains the nucleu chromosomes made of DNA. Th highlighted again, emphasizing t  From HAPLOID to DIPLOID The chromosomes replicate before a cell divides to make sure that each daughter cell contains a complete set of chromosomes. All living things perpetuate their own kind and pass their characteristics to their offspring. (Reproduction) Cell division – sex cell or gametes undergo to maintain the chromosome number of their species.  From HAPLOID to DIPLOID Meiosis – is a specialized form of cell division that occurs in organisms that reproduce sexually. It produces reproductive cells: sperm cell in male, egg cell in female, and spores in plants and fungi. - it results in daughter cells that possess half the number of chromosomes of the parent cell.  From HAPLOID to DIPLOID Sex cells: haploid (n) = 23 chromosomes in gametes : diploid (2n) = 46 chromosomes in gametes (Complete) During fertilization, the sperm carries only half the number of chromosomes and unites with the egg cell that is also haploid The resulting zygote is said to be diploid (2n)  All cells of the body, except the sperm and egg cell, contains a complete set of chromosomes. The first 22 pairs are body chromosomes or autosomes and the 23rd pair makes up the sex chromosomes.  Variation and Inherited Hum Traits The combination of sex cells during fertilization results in variation in the offspring. Meiotic Process (1st stage of Meiosis) Variation and Inherited Hum Traits Chiasmata – points where chromosomes cross over Segregation – it allows homologous chromosomes to separate so that they will have an equal chance of being passed on to the next generation. Variation and Inherited Hum Traits Variation may also be caused by the permanent change in DNA sequence called mutation. Mutation may be brought by different factors; environmental, or errors in cell division  Mutation Mutation may either somatic or germline Somatic mutation – occurs in any body cell except the reproductive cells. Germline mutation – also known as germinal mutation, occurs in reproductive cells - hereditary mutation  Variation and Inherited Hum Traits Most genes have two or more variations called alleles. Alleles – any one of two or more genes that may occur alternatively at a given site (locus) on a chromosome. - it may occur in pairs, or there may be multiple alleles affecting the expression of a particular trait.  Genotype and Phenotype Genotype – is an actual set of genes carried by an organism Phenotype – expression or manifestation of an organism’s genotype Homozygous and Heterozygous Homozygous – if the alleles for a trait are the same Heterozygous – when the two inherited alleles for a particular trait are different  Dominant and Recessive Traits Dominant trait – expresses itself and masks the effect of the other allele for the same trait Recessive trait – is one that is masked by the presence of the dominant allele and will only manifest if the organism is homozygous for the recessive allele  Mother Mother B b Father B BB Bb Father b Bb bb