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Genetics: The Science of Heredity Chapter 4 7 th Grade Science.

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Presentation on theme: "Genetics: The Science of Heredity Chapter 4 7 th Grade Science."— Presentation transcript:

1 Genetics: The Science of Heredity Chapter 4 7 th Grade Science

2 Mendel’s Work ______________ - “Father of Genetics” – A priest that conducted experiments in his garden that revolutionized the study of heredity. – ___________ - the passing of physical characteristics from parents to offspring – Mendel used pea plants to observe _________ of pea plants. – _________ - a characteristic that an organism can pass on to its offspring through its genes. Gregor Mendel Heredity traits

3 Mendel and Heredity Mendel experimented with hundreds of pea plants to understand the process of ________. ________ - the scientific study of heredity. Mendel “crossed” pea plants with contrasting ________ and observed the outcomes of traits in the offspring. Mendel started his experiments with ________ pea plants or plants that have had the same trait for many generations. heredity Genetics traits purebred

4 Crossing Pea Plants __________ short pea plants come always come from short parent plants. Purebred

5 Mendel’s Experiments

6 Generations and Offspring _____________ - parent generation _________________ - the offspring from the first parent generation. “Filia” comes from the Latin word meaning son or daughter. This generation is noted as __ - all of the plants in this generation were tall. _________ - Mendel allowed the plants in the f₁ generation to self pollinate. The plants in the f₂ generation - the result was a mix of short and tall plants P generation First “filial” generation f₁ F₂ generation

7 Mendel’s Conclusion Mendel’s Conclusions included: – Individual factors or sets of _________ information controls the __________ of traits in peas. The factors that control each trait exist in _____ - one from the _______ parent and one from the _______parent. One factor in each pair can mask or hide the other factor. genetic inheritance pairs female male

8 Dominant and Recessive ________- factors that control a trait. _____ - different forms of the gene Offspring inherit one _______ from each parent – one could be tall and the other could be short, both could be tall, both could be short – it depends on the ________ information from the parent. ____________ - the trait that always shows up in the organism when the allele is present ____________ - hidden whenever the dominant allele is present Dominant allele Alleles Allele genetic Gene Recessive Allele

9 Genetics of Pea Plants

10 Alleles in Mendel’s Crosses ___________ - only pea plants that inherit two recessive alleles for short stems will be short. _________ - organism has two different alleles for a trait. ________ alleles mask the ________ alleles. A dominant allele is represented by a ______ letter. Recessive alleles are represented by ________ letters. Purebred short hybrid Dominantrecessive capital Lower case

11 Pea Plant traits

12 Probability and Heredity ________ - a number that describes how likely it is that an event will occur. Not necessarily what will occur. Example: coin toss – the more tosses you make, the closer the actual results will be to the results predicted by probability. Each toss yields a result that is __________ of all other tosses. probability independent

13 Probability and Genetics Mendel was the first scientist to recognize that the principles of __________ can be used to predict the results of ___________. ____________ - a chart that shows all the possible combinations of ________ that can result from a genetic cross. The boxes in the Punnett Square represent the possible alleles that the offspring can _______. probability Genetic crosses Punnett Square alleles inherit

14 Punnett Square Examples

15 Phenotypes and Genotypes ____________ - an organisms physical appearance or visible traits. ___________ - an organisms genetic makeup, or allele combinations. ___________ - two identical alleles for a trait ___________ - two different alleles for a trait Mendel used the term _________ to describe __________ pea plants. phenotype genotype homozygous heterozygous hybrid heterozygous

16 Codominance __________ - the alleles are neither dominant nor recessive – both alleles are expressed in the offspring. Codominance

17 Chromosomes and Inheritance _______________________ - genes are carried from parents to their offspring on chromosomes. _______ - the process by which the number of chromosomes is reduced by half to form sex cells – ____________. – Chromosome pairs separate and are distributed to two different cells. – The resulting sex cells have only half as many chromosomes as the other cells in the organism. Chromosome Theory of inheritance meiosis Sperm and egg

18 Meiosis

19 Meiosis and Punnett Square _____________-show the events that occur in meiosis. – When the _______________ separate and go into two different ________, so do the _________ carried on each chromosome. – Punnett Squares show the possible allele combinations after __________. Punnett Square Chromosome pairs Sex cellsallele fertilization

20 Punnet Square

21 Genes The body cells of humans contain ____ chromosome pairs. Chromosomes are made up of many ______ joined together like beads on a string. Body cells contain between _______________ Each ______ controls a _____ The _______ are lined up in the same order on each ___________. 23 genes 20,000-25,000 genes genetrait genes chromosome

22 Chromosomes and Genes

23 The DNA Connection _______ - control the production of ________ in an organisms cells. __________ - determine the size, shape, color and many other traits of an organisms. A gene is a section of _______ molecule that contains the information to code for a specific __________. Each _______ is located in a place on a _________ geneproteins DNA protein gene chromosome

24 Order of Bases _________contains the _____ that determines the structure of the ______. ___________ form a ___________ that specifies what type of ______ will be produced. _________ - long chains molecules of individual __________. A group of _____________ codes for one specific __________. genecode protein Nitrogen BasesGenetic code protein proteins Amino acids 3 DNA bases Amino acid

25 How cells make proteins ___________ - production of proteins – cells use the information from a gene on a chromosome to produce a specific _______. Protein synthesis takes place on the ________ in the __________ of the cell. ____ - ribonucleuc acid – “Messenger” carries the genetic code from the DNA inside of the nucleus to the ________. Protein Synthesis protein ribosome cytoplasm RNA cytoplasm

26 DNA / RNA DNA has ________, RNA has _________ Both DNA and RNA contain ___________ but they are different DNA has four bases - ___________ RNA has ____________ 2 types of RNA - ____________ and ____________ 2 strands1 strand Sugar molecules A, T, C, G A, C, G and uracil Messenger RNA Transfer RNA

27 RNA ____________ - copies the coded message from the DNA in the nucleus and carries the message to the ribosome in the cytoplasm. ____________ - carries amino acids to the ribosomes and adds them to the growing protein Messenger RNA Transfer RNA

28 Translating the Code 1. Message transferred to the messenger RNA 2. Messenger RNA attaches to the Ribosome 3. Transfer RNA attaches to the Messenger RNA 4. Protein Production continues. Page

29 Mutations _________ - any change in a gene or chromosome. Mutations can cause a cell to produce an incorrect protein during ____________ - this change can effect the organisms trait or phenotype. Mutations that occur in sex cells can be passed on to _______. Other mutations are not passed on. Mutation Protein synthesis offspring


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