Presentation on theme: "4.1 Living Things Inherit Traits in Patterns"— Presentation transcript:
1 4.1 Living Things Inherit Traits in Patterns We know the offspring produced by sexual reproduction have genetic material from two parentsOffspring get traits from parentsBut not all traits
2 4.1 Living Things Inherit Traits in Patterns Inherited traitcharacteristic passed down from parentsborn with itdetermined by genesAcquired Traitcharacteristic developed during life
3 4.1 Living Things Inherit Traits in Patterns In the table below, write yes if the trait is the result of heredity or no if it is not.TraitResult of Heredity?Blonde hairAble to speak EnglishAble to ride a bikeGreen eyesYesNoNoYes
4 4.1 Living Things Inherit Traits in Patterns If a mother works out as a body builder for many years, are the chances high that her offspring will inherit strong muscles? Why or why not?The offspring has the potential for strong muscles, but a muscle grows if it is worked. The child will have to do the same workouts to get big muscles, he/she will not be born with them.
5 4.1 Living Things Inherit Traits in Patterns Inherited traits are controlled or coded for by genesgenes – unit of heredity that codes for a particular traitexamples:Eye colorHair colorheredityPassing of genes from parent to offspring
6 There are various forms of the same gene 4.1 Living Things Inherit Traits in PatternsThere are various forms of the same geneExample –Eye color has several variationsbrownbluegreenhazelThese variations are called alleles
7 Example: Brown or blonde hair What is the gene? What is the allele? 4.1 Living Things Inherit Traits in PatternsExample:Brown or blonde hairWhat is the gene?What is the allele?
8 4.1 Living Things Inherit Traits in Patterns Example:Brown or blonde hairWhen working with heredity, genes are assigned a letterThe gene would code for hair color and could be represented by the letter HSo each allele would be a variation of the letter H to represent a variation of the geneH = brownh = blonde
9 4.1 Living Things Inherit Traits in Patterns Capital letter represent dominant alleles and lower case letters represent recessive allelesDominant – an allele that determines the phenotype of an individual organism when two different copies are present in the genotypeRecessive – an allele that is not expressed when combined with a dominant form of a gene. It is only expressed in the phenotype when both alleles present in the genotype are recessive
10 4.1 Living Things Inherit Traits in Patterns If a dominant allele is present, the trait of the dominant allele shows. Whether one or two dominant alleles are presentIf there is no dominant allele, and both alleles present are recessive, then the recessive trait shows
11 Dominant traits are expressed even if only one allele codes for it. 4.1 Living Things Inherit Traits in PatternsWhy are some parents’ traits expressed in their offspring while others are not?Dominant traits are expressed even if only one allele codes for it.If a trait is recessive, both alleles must be recessive for it to show in the phenotype.
12 Eye color is represented by the letter E 4.1 Living Things Inherit Traits in PatternsThe combination of alleles is the genotypeThe trait that shows as a result of the genotype is the phenotypeExample -Eye color is represented by the letter EE = browne = blueEEEeeeGenotypesThe resulting phenotypesBlue eyesBrown eyesBrown eyes
14 4.1 Living Things Inherit Traits in Patterns A science student crosses a purebred regular height pea plant with a dwarf height plant. Four new pea plants are grown. Draw the four pea plants in the space below. Be sure to make them the right height.
15 4.2 Patterns of Heredity can be Predicted Unit AChapter 4
16 Punnett Squareschart used to show all of the ways genes from two parents can combine and be passed on to offspringshows possible outcomes for inheritance - the possible combinations of parents allelesthe top part shows one parent’s alleles for a traitHHHhthe side shows the other parent’s alleles for a traitHHHHhhHhhh
17 1. How is the symbol for each allele the same? Each allele for a trait is symbolized by the same letter
18 2. How can you tell which allele is dominant? Dominant alleles are symbolized by capital letters.
19 3. How can you tell which allele is recessive? Recessive alleles are symbolized by lower case letters.
20 4. Which trait is dominant here? Regular height (H)
21 5. Which trait is recessive here? Dwarf height (h)
22 The alleles of one possible offspring 6. What does each box show?The alleles of one possible offspring
23 4.3 Meiosis is a special form of cell division Sexual reproduction involves two parentsEach parent produces specialized cells that contain half the amount of genetic material a cells needsThe specialized cells contain one allele for each gene and are called haploid cells
24 4.3 Meiosis is a special form of cell division Haploid cellscontain half the usual number of chromosomes (one chromosome from each pair of chromosomes)1n cellsalso known as gametesegg – gamete of the femalesperm – gamete of the male
25 4.3 Meiosis is a special form of cell division The cell resulting from a sperm and egg combining has a full set of DNAThey have two alleles per gene and are called diploid cells
26 4.3 Meiosis is a special form of cell division Diploid cellscontains the full number of chromosomes (both chromosomes in a pair)2n cells
27 4.3 Meiosis is a special form of cell division Example: In humanshaploid cells have 23 chromosomesdiploid cells have 46 chromosomes
28 4.3 Meiosis is a special form of cell division special kind of cell division that produces haploid cellsinvolves two divisions of a single celltakes place only in reproductive tissues of an organismnecessary for sexual reproduction
29 4.3 Meiosis is a special form of cell division during sexual reproduction, the gametes (1n) combine to become a 2n cell that grows into the offspring:genetic information from the mothercombines withgenetic information from the fatherto formA new cellfertilization – sperm and egg combine to form one new cellthe new cell that is formed has half its genetic information from its mother and half from its father